Human prohormone convertase 4

ABSTRACT

The present invention provides polynucleotide and polypeptide molecules for a novel human prohormone convertase 4. The polynucleotides encoding human prohormone convertase 4, are located on chromosome 19, and may, for example, be used to identify a region of the genome associated with human disease states. The present invention also includes methods for producing the protein and antibodies thereto.

The present application is a divisional application of co-pending U.S. patent application Ser. No. 09/071,101 filed May 1, 1998 (now U.S. Pat. No. 6,013,503) which is related to Provisional Application Ser. No. 60/044,015 filed May 6, 1997. Under 35 U.S.C. § 119(e)(1), this application claims benefit of said Provisional Application.

BACKGROUND OF THE INVENTION

Many proteins and hormones, synthesized as precursors, are processed into their mature forms by highly-specific proteolytic enzymes of the prohormone convertase family. This family of mammalian endoproteases carries out intracellular cleavage at the COOH-terminal side of dibasic sites within their substrate polypeptides. Members of this prohormone convertase (PC) family are Ca⁺⁺ -dependent serine proteases related to the yeast dibasic-specific endoprotease Kex2 (Smeekins, S. P., Bio/Technology 11: 182-186, 1993). Moreover, the catalytic domains thereof are organized similarly to bacterial subtilisins. At least six mammalian prohormone convertases have been found including PC2, PC3/PC1, PC4, PC5/6 furin/PACE and PACE4 (Smeekins, S. P., ibid., Seidah, N. G. et al., Biochimie (France) 76: 197-209, 1994).

Mammalian prohormone convertases act on a wide variety of precursor molecules having an array of biological activities. The proinsulin prohormone was the first substrate precursor identified. Subsequently, over 150 substrates have been found in organisms from yeast to mammals; including neuropeptides, peptide hormones, growth factors and their receptors, plasma and coagulation proteins, retroviral envelope proteins and cellular toxins, e.g., anthrax. Cleavage sites include basic amino acids, with cleavage occurring at paired basic residues, usually after Lys-Arg or Arg-Arg and more rarely Arg-Lys or Lys--Lys (Smeekins, S. P., ibid.).

The prohormone convertase family exhibits tissue-specific expression and cellular compartmentalization, which may relate to biological function. For example, PC1/3 and PC2 are solely expressed in neuroendocrine tissues. Biological activities of these proteins are localized to the regulated secretory pathway in neuroendocrine cells, specifically in secretory granules; and both play important roles in processing precursors in the granules such as proglucagon, proopiomelanocortin (POMC) and proinsulin. Thus, intracellular localization and tissue specificity appear to reflect where the biological activities of these endoproteases are manifested.

PC4 exhibits highly specific tissue-selectivity of gene expression. PC4 has been isolated from mice and rats and is solely expressed in the testis. In mice, PC4 gene expression occurs around the 20th day of gestation corresponding with the first stages of spermatogenesis. High PC4 mRNA expression levels are found in germ cells but not in Leydig, Sertoli, or peritubular cells. In situ hybridization demonstrates mRNA expression in the pachytene spermatocytes and the round spermatids, but not in elongating spermatids (N.G. Seidah et al., Mol. Endocrinol. 6: 1559-1570, 1992). Moreover, in both rat and mouse, three PC4 mRNAs are observed; these RNAs are probably derived from differential splicing and/or exon skipping events. The biological function of murine and rat PC4 proteins derived from the principle or alternatively spliced forms is unknown.

Spermatogenesis is a sequential process taking place in the seminiferous tubules, where germ (or sperm) cells ultimately mature into spermatozoa. Peptides produced within the testis are potential paracrine and autocrine factors mediating interactions between testicular cells. Most of these known potential peptide substrates are produced within Leydig and Sertoli cells which are non-germ cells. Sertoli cells, located within the seminiferous tubules, are in contact with the germ cells and may directly produce testis-specific factors that influence germ cell maturation. Other factors that influence germ cells may be paracrine or endocrine factors; many of these molecules produced outside the seminiferous tubules are transported into the germ cell microenvironment by transport and binding proteins expressed by the Sertoli cells. In addition, paracrine factors that cross the cellular barrier and enter the sperm cell microenvironment include molecules secreted from Leydig cells. Leydig cells are located in the interstitial space found between the seminiferous tubules, and produce several factors that may play important roles in the maturation process, such as testosterone, Leydig factor, IGF-1, inhibin and prohibin. These and other factors may act specifically during a defined stage in the spermatogenic cycle. Moreover, some peptide hormones expressed in germ cells, located in close proximity to Sertoli cells, are potential paracrine and autocrine factors that mediate interactions between testicular cells. For example, the opioid peptides, POMC and proenkephalin, are expressed and presumably processed in germ cells. Interestingly, murine proenkephalin has a similar mRNA expression profile to murine PC4 during spermatogenesis (S. Torii, et al., FEBS Let. 316: 12-16, 1993). The stage-specific expression of murine PC4 implicates a biological role in processing prohormone factors from the testis. Although a role for PC4 in spermatogenesis is suggested, the function of PC4 is unknown.

Thus, the human homologue is sought. The present invention advantageously provides the isolation of a human homologue to murine PC4.

SUMMARY OF THE INVENTION

The present invention provides an isolated polynucleotide encoding a human prohormone convertase 4 polypeptide comprising a sequence of amino acid residues that is at least 90% identical to an amino acid sequence selected from the group consisting of: (a) the amino acid sequence as shown in SEQ ID NO:2 from amino acid number 114 (Ser) to amino acid number 443 (Ala); (b) the amino acid sequence as shown in SEQ ID NO:2 from amino acid number 114 (Ser) to amino acid number 755 (Thr); (c) the amino acid sequence as shown in SEQ ID NO:2 from amino acid number 20 (Arg) to amino acid number 755 (Thr); and

(d) the amino acid sequence as shown in SEQ ID NO:2 from amino acid number 1 (Met) to amino acid number 755 (Thr).

Within another embodiment, the isolated human prohormone convertase 4 polynucleotide disclosed above is selected from the group consisting of: (a) a polynucleotide sequence as shown in SEQ ID NO:1 from nucleotide 400 to nucleotide 1389; (b) a polynucleotide sequence as shown in SEQ ID NO:1 from nucleotide 400 to nucleotide 2325; (c) a polynucleotide sequence as shown in SEQ ID NO:1 from nucleotide 118 to nucleotide 2325; and (d) a polynucleotide sequence as shown in SEQ ID NO:1 from nucleotide 61 to nucleotide 2325. Within another embodiment, the isolated human prohormone convertase 4 polynucleotide disclosed above comprises nucleotide 1 to nucleotide 2265 of SEQ ID NO:3. Within another embodiment, the isolated human prohormone convertase 4 polynucleotide disclosed above encodes a human prohormone convertase 4 polypeptide consisting essentially of a sequence of amino acid residues that is at least 90% identical to an amino acid sequence as shown in SEQ ID NO:2 from amino acid number 20 (Arg) to amino acid number 755 (Thr). Within another embodiment, the isolated polynucleotide disclosed above encodes a human prohormone convertase 4 polypeptide consisting essentially of a sequence of amino acid residues as shown in SEQ ID NO:2 from amino acid number 20 (Arg) to amino acid number 755 (Thr).

Within a second aspect, the present invention provides an expression vector comprising the following operably linked elements: a transcription promoter; a DNA segment encoding a prohormone convertase polypeptide that is at least 90% identical to an amino acid sequence as shown in SEQ ID NO:2 from amino acid number 20 (Arg) to amino acid number 755 (Thr); and a transcription terminator. Within another embodiment, the expression vector disclosed above further comprises a secretory signal sequence operably linked to the DNA segment.

Within a third aspect, the present invention provides a cultured cell into which has been introduced an expression vector as disclosed above, wherein the cell expresses a polypeptide encoded by the DNA segment.

Within another aspect, the present invention provides a DNA construct encoding a fusion protein, the DNA construct comprising: a first DNA segment encoding a polypeptide that is at least 90% identical to a sequence of amino acid residues selected from the group consisting of: (a) the amino acid sequence of SEQ ID NO: 2 from residue number 1 (Met), to residue number 21 (Pro); (b) the amino acid sequence of SEQ ID NO: 2 from residue number 20 (Arg), to residue number 113 (Arg); (c) the amino acid sequence of SEQ ID NO: 2 from residue number 114 (Ser), to residue number 443 (Ala); (d) the amino acid sequence of SEQ ID NO: 2 from residue number 444 (Arg), to residue number 561 (Tyr); (e) the amino acid sequence of SEQ ID NO: 2 from residue number 562 (Tyr), to residue number 755 (Thr); (f) the amino acid sequence of SEQ ID NO: 2 from residue number 114 (Ser), to residue number 755 (Thr); (g) the amino acid sequence of SEQ ID NO: 2 from residue number 20 (Arg), to residue number 755 (Thr); and at least one other DNA segment encoding an additional polypeptide, wherein the first and other DNA segments are connected in-frame; and encode the fusion protein. Within another embodiment, the present invention provides a fusion protein produced by a method comprising: culturing a host cell into which has been introduced a vector comprising the following operably linked elements: (a) a transcriptional promoter; (b) a DNA construct encoding a fusion protein as disclosed above; and (c) a transcriptional terminator; and recovering the protein encoded by the DNA segment.

Within another aspect, the present invention provides an isolated polypeptide comprising a sequence of amino acid residues that is at least 90% identical to an amino acid sequence selected from the group consisting of: (a) the amino acid sequence as shown in SEQ ID NO:2 from amino acid number 114 (Ser) to amino acid number 443 (Ala); (b) the amino acid sequence as shown in SEQ ID NO:2 from amino acid number 114 (Ser) to amino acid number 755 (Thr); (c) the amino acid sequence as shown in SEQ ID NO:2 from amino acid number 20 (Arg) to amino acid number 755 (Thr); and (d) the amino acid sequence as shown in SEQ ID NO:2 from amino acid number 1 (Met) to amino acid number 755 (Thr). Within another embodiment, the isolated polypeptide disclosed above consists essentially of a sequence of amino acid residues that is at least 90% identical to an amino acid sequence as shown in SEQ ID NO:2 from amino acid number 20 (Arg) to amino acid number 755 (Thr). Within another embodiment, the isolated polypeptide disclosed above, is as shown in SEQ ID NO:2 from amino acid number 20 (Arg) to amino acid number 755 (Thr).

Within another aspect, the present invention provides a method of producing a human prohormone convertase 4 polypeptide comprising: culturing a cell as disclosed above; and isolating the human prohormone convertase polypeptide produced by the cell.

Within another aspect, the present invention provides a method of determining polypeptide prohormone substrates of a human prohormone convertase 4 polypeptide comprising: culturing a cell into which has been introduced an expression vector as disclosed above, wherein the cell expresses a human prohormone convertase polypeptide encoded by the DNA segment and co-expresses a test substrate prohormone polypeptide; and detecting cleavage products resulting from cleavage of the test substrate by the human prohormone convertase 4. Within another embodiment, the method of determining polypeptide prohormone substrates of a human prohormone convertase 4 polypeptide comprises: combining in vitro, prohormone convertase 4 polypeptide with a test substrate polypeptide; and detecting cleavage products resulting from cleavage of the test substrate by the human prohormone convertase 4 polypeptide.

Within another aspect, the present invention provides a method of detecting, in a test sample, the presence of a modulator of human prohormone convertase polypeptide activity, comprising: culturing a cell into which has been introduced an expression vector as disclosed above, wherein the cell expresses the human prohormone convertase polypeptide encoded by the DNA segment and co-expresses a known indicator prohormone polypeptide substrate, in the presence and absence of a test sample; and comparing levels of cleavage products resulting from cleavage of the substrate by the human prohormone convertase polypeptide, in the presence and absence of the test sample, by a biological or biochemical assay; and determining from the comparison, the presence of the modulator of human prohormone convertase polypeptide activity in the test sample.

Within another aspect, the present invention provides a method of producing an antibody to human prohormone convertase 4 polypeptide comprising: inoculating an animal with a polypeptide selected from the group consisting of: (a) a polypeptide consisting of 9 to 755 amino acids, wherein the polypeptide is at least 90% identical to a contiguous stretch of amino acids in SEQ ID NO:2 from amino acid number 20 (Arg) to amino acid number 755 (Ser); (b) a polypeptide as disclosed above; (c) a polypeptide with an amino acid sequence that is at least 90% identical to residue number 444 (Arg), to residue number 561 (Tyr) of SEQ ID NO:2; and (d) a polypeptide with an amino acid sequence that is at least 90% identical to residue number 562 (Tyr), to residue number 755 (Thr) of SEQ ID NO:2, wherein the polypeptide elicits an immune response in the animal; and isolating the antibody from the animal. Within another embodiment the antibody produced by the method disclosed above binds to a human prohormone convertase 4 polypeptide. Within another embodiment, the antibody disclosed above is a monoclonal antibody.

Within another aspect, the present invention provides an antibody which specifically binds to a polypeptide as disclosed above.

These and other aspects of the invention will become evident upon reference to the following detailed description of the invention and attached drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE is a multiple alignment of human PC1, human PC2, rat PC4, murine PC4, a novel human PC4 of the present invention, murine furin, and human furin.

DETAILED DESCRIPTION OF THE INVENTION

Prior to setting forth the invention in detail, it may be helpful to the understanding thereof to define the following terms:

The term "affinity tag" is used herein to denote a polypeptide segment that can be attached to a second polypeptide to provide for purification or detection of the second polypeptide or provide sites for attachment of the second polypeptide to a substrate. In principal, any peptide or protein for which an antibody or other specific binding agent is available can be used as an affinity tag. Affinity tags include a poly-histidine tract, protein A (Nilsson et al., EMBO J. 4:1075, 1985; Nilsson et al., Methods Enzymol. 198:3, 1991), glutathione S transferase (Smith and Johnson, Gene 67:31, 1988), Glu--Glu affinity tag (Grussenmeyer et al., Proc. Natl. Acad. Sci. USA 82:7952-4, 1985), substance P, Flag™ peptide (Hopp et al., Biotechnology 6:1204-1210, 1988; available from Eastman Kodak Co., New Haven, Conn.), streptavidin binding peptide, or other antigenic epitope or binding domain. See, in general, Ford et al., Protein Expression and Purification 2: 95-107, 1991. DNAs encoding affinity tags are available from commercial suppliers (e.g., Pharmacia Biotech, Piscataway, N.J.).

The term "allelic variant" is used herein to denote any of two or more alternative forms of a gene occupying the same chromosomal locus. Allelic variation arises naturally through mutation, and may result in phenotypic polymorphism within populations. Gene mutations can be silent (no change in the encoded polypeptide) or may encode polypeptides having altered amino acid sequence. The term allelic variant is also used herein to denote a protein encoded by an allelic variant of a gene.

The terms "amino-terminal" and "carboxyl-terminal" are used herein to denote positions within polypeptides. Where the context allows, these terms are used with reference to a particular sequence or portion of a polypeptide to denote proximity or relative position. For example, a certain sequence positioned carboxyl-terminal to a reference sequence within a polypeptide is located proximal to the carboxyl terminus of the reference sequence, but is not necessarily at the carboxyl terminus of the complete polypeptide.

The term "cleavage products" is used to denote prohormone polypeptide fragments resulting from cleavage of the unprocessed prohormone polypeptide by a prohormone convertase.

The term "complement/anti-complement pair" denotes non-identical moieties that form a non-covalently associated, stable pair under appropriate conditions. For instance, biotin and avidin (or streptavidin) are prototypical members of a complement/anti-complement pair. Other exemplary complement/anti-complement pairs include receptor/ligand pairs, antibody/antigen (or hapten or epitope) pairs, sense/antisense polynucleotide pairs, and the like. Where subsequent dissociation of the complement/anti-complement pair is desirable, the complement/anti-complement pair preferably has a binding affinity of <10⁹ M⁻¹.

The term "complement of a polynucleotide molecule" is a polynucleotide molecule having a complementary base sequence and reverse orientation as compared to a reference sequence. For example, the sequence 5' ATGCACGGG 3' is complementary to 5' CCCGTGCAT 3'.

The term "degenerate nucleotide sequence" denotes a sequence of nucleotides that includes one or more degenerate codons (as compared to a reference polynucleotide molecule that encodes a polypeptide). Degenerate codons contain different triplets of nucleotides, but generally encode the same amino acid residue (i.e., GAU and GAC triplets each encode Asp).

A "DNA construct" is a single or double stranded, linear or circular DNA molecule that comprises segments of DNA combined and juxtaposed in a manner not found in nature. DNA constructs exist as a result of human manipulation, and include clones and other copies of manipulated molecules.

A "DNA segment" is a portion of a larger DNA molecule having specified attributes. For example, a DNA segment encoding a specified polypeptide is a portion of a longer DNA molecule, such as a plasmid or plasmid fragment, that, when read from the 5' to the 3' direction, encodes the sequence of amino acids of the specified polypeptide.

The term "expression vector" is used to denote a DNA molecule, linear or circular, that comprises a segment encoding a polypeptide of interest operably linked to additional segments that provide for its transcription. Such additional segments include promoter and terminator sequences, and may also include one or more origins of replication, one or more selectable markers, an enhancer, a polyadenylation signal, etc. Expression vectors are generally derived from plasmid or viral DNA, or may contain elements of both.

The term "isolated", when applied to a polynucleotide, denotes that the polynucleotide has been removed from its natural genetic milieu and is thus free of other extraneous or unwanted coding sequences, and is in a form suitable for use within genetically engineered protein production systems. Such isolated molecules are those that are separated from their natural environment and include cDNA and genomic clones. Isolated DNA molecules of the present invention are free of other genes with which they are ordinarily associated, but may include naturally occurring 5' and 3' untranslated regions such as promoters and terminators, and the like. The identification of associated regions will be evident to one of ordinary skill in the art (see for example, Dynan and Tijan, Nature 316:774-78, 1985).

An "isolated" polypeptide or protein is a polypeptide or protein that is found in a condition other than its native environment, such as apart from blood and animal tissue. In a preferred form, the isolated polypeptide is substantially free of other polypeptides, particularly other polypeptides of animal origin. It is preferred to provide the polypeptides in a highly purified form, i.e., greater than 95% pure, more preferably greater than 99% pure. When used in this context, the term "isolated" does not exclude the presence of the same polypeptide in alternative physical forms, such as dimers or alternatively glycosylated or derivatized forms.

The term "operably linked", when referring to DNA segments, indicates that the segments are arranged so that they function in concert for their intended purposes, e.g. transcription initiates in the promoter and proceeds through the coding segment to the terminator.

The term "ortholog" denotes a polypeptide or protein obtained from one species that is the functional counterpart of a polypeptide or protein from a different species. Sequence differences among orthologs are the result of speciation.

"Paralogs" are distinct but structurally related proteins made by an organism. Paralogs are believed to arise through gene duplication. For example, (α-globin, β-globin, and myoglobin are paralogs of each other.

A "polynucleotide" is a single- or double-stranded polymer of deoxyribonucleotide or ribonucleotide bases read from the 5' to the 3' end. Polynucleotides include RNA and DNA, and may be isolated from natural sources, synthesized in vitro, or prepared from a combination of natural and synthetic molecules. Sizes of polynucleotides are expressed as base pairs (abbreviated "bp"), nucleotides ("nt"), or kilobases ("kb"). Where the context allows, the latter two terms may describe polynucleotides that are single-stranded or double-stranded. When the term is applied to double-stranded molecules it is used to denote overall length and will be understood to be equivalent to the term "base pairs". It will be recognized by those skilled in the art that the two strands of a double-stranded polynucleotide may differ slightly in length and that the ends thereof may be staggered as a result of enzymatic cleavage; thus all nucleotides within a double-stranded polynucleotide molecule may not be paired. Such unpaired ends will in general not exceed 20 nt in length.

A "polypeptide" is a polymer of amino acid residues joined by peptide bonds, whether produced naturally or synthetically. Polypeptides of less than about 10 amino acid residues are commonly referred to as "peptides".

The term "promoter" is used herein for its art-recognized meaning to denote a portion of a gene containing DNA sequences that provide for the binding of RNA polymerase and initiation of transcription. Promoter sequences are commonly, but not always, found in the 5' non-coding regions of genes.

A "protein" is a macromolecule comprising one or more polypeptide chains. A protein may also comprise non-peptidic components, such as carbohydrate groups. Carbohydrates and other non-peptidic substituents may be added to a protein by the cell in which the protein is produced, and will vary with the type of cell. Proteins are defined herein in terms of their amino acid backbone structures; substituents such as carbohydrate groups are generally not specified, but may be present nonetheless.

The term "secretory signal sequence" denotes a DNA sequence that encodes a polypeptide (a "secretory peptide") that, as a component of a larger polypeptide, directs the larger polypeptide through a secretory pathway of a cell in which it is synthesized. The larger polypeptide is commonly cleaved to remove the secretory peptide during transit through the secretory pathway. A secretory signal sequence will direct a polypeptide into the secretory pathway of a cell but may or may not target a polypeptide containing the sequence to be actually secreted from the cell.

The term "splice variant" is used herein to denote alternative forms of RNA transcribed from a gene. Splice variation arises naturally through use of alternative splicing sites within a transcribed RNA molecule, or less commonly between separately transcribed RNA molecules, and may result in several mRNAs transcribed from the same gene. Splice variants may encode polypeptides having altered amino acid sequence. The term splice variant is also used herein to denote a protein encoded by a splice variant of an mRNA transcribed from a gene.

Molecular weights and lengths of polymers determined by imprecise analytical methods (e.g., gel electrophoresis) will be understood to be approximate values. When such a value is expressed as "about" X or "approximately" X, the stated value of X will be understood to be accurate to ±10%.

Teachings of all references cited herein are in their entirety incorporated by reference.

The present invention is based in part upon the discovery of a novel DNA sequence that encodes a protein with homology to the prohormone convertase family (e.g., murine and rat PC4, PC2, PC1, furin). The DNA sequence was designated human prohormone convertase 4, abbreviated herein as "human PC4." Analysis of the tissue distribution of the mRNA corresponding to this novel cDNA showed that mRNA expression was restricted to the testis. Such tissue-specific expression indicates a role as a prohormone convertase that fully or partially processes the prohormone polypeptides of growth or differentiation factors to mature or active forms for testis-specific and non-testis cell types.

Mammalian prohormone convertases share common structural features. See, Smeekins, S. P., ibid., and Seidah, N. Methods in Enz., 244: 175-188, 1995, for review. All contain an N-terminal secretory peptide that directs the protein into the secretory pathway. This region is followed by the Homo-A domain, likely involved in protease folding. Removal of the Homo-A domain by autocatalysis is essential for proteolytic activation. Following the Homo-A domain is the catalytic domain, which is essential for activity. The catalytic domain has the highest amino acid sequence identity with the bacterial subtilisin catalytic region. Adjacent to the catalytic domain is the Homo-B domain, which is also essential for enzymatic activity. Beyond this region, at the C-terminal end, prohormone convertases structurally diverge. The functional role for the C-terminal regions is unknown but is likely involved in cell and organelle-specific targeting of mammalian prohormone convertases.

The present invention provides for a novel human prohormone convertase. Analysis of a human cDNA encoding a prohormone convertase (SEQ ID NO: 1) revealed an open reading frame encoding 755 amino acids (SEQ ID NO: 2), comprising a putative secretory peptide (see, SEQ ID NO: 2 from residue 1 (Met) to residue 19 (Val)) and a mature polypeptide (see, SEQ ID NO:2 from residue 20 (Arg) to residue 755 (Thr)). As shown in the FIGURE, the mature polypeptide has homology with other members of the Kex2 family of endoproteases, which includes rat and murine PC4, human furin, human PC1 and human PC2. As described above, this protein family is characterized by a conserved subtilisin-like catalytic domain (see, SEQ ID NO: 2 from residue 114 (Ser) to residue 443 (Ala) ) which is flanked at the NH₂ -- and COOH-terminal ends by regions that are less conserved, referred to as Homo-A (see, SEQ ID NO: 2 from residue 20 (Arg) to residue 113 (Arg) ) and Homo-B (see, SEQ ID NO: 2 from residue 444 (Arg) to residue 561 (Tyr)) domains respectively (Nakayama et al., J. Biochem (Tokyo), 109: 803-806, 1991). The active site Asp, His, and Ser residues and catalytically important Asn residue present in rat and murine PC4 are conserved in the human PC4 (see, SEQ ID NO: 2, residues Asp-158, His-198, Ser-372 and Asn-300). The site of signal peptidase cleavage is predicted to occur after residue 19 (Val), based on alignment of the human prohormone convertases. The conserved Arg-Gly-Asp sequence (see, SEQ ID NO: 2, residues number 503 to number 505), found in all known mammalian prohormone convertases, is present in human PC4 (Nakayama, ibid., and references therein). Human PC4 is predicted to be synthesized as a precursor enzyme (zymogen) which undergoes autocatalytic cleavage at the C-terminal side of an Arg-Arg-Val-Lys-Arg (SEQ ID NO:4; see also, SEQ ID NO: 2 from residue number 109 (Arg) to residue number 113 (Arg)) sequence to yield an active enzyme. A similar zymogen activation sequence is observed for Kex2 and rat PC4 (Nakayama et al., J. Biochem (Tokyo), 109: 803-806, 1991). The C-terminal domain (see, SEQ ID NO: 2 from residue 562 (Tyr) to residue 755 (Thr)) unique to human PC4 has the highest sequence identity to furin. The function of this domain may be involved in cell and organelle-specific targeting.

The highly conserved amino acids in, for example, the subtilisin-like catalytic domain of human PC4, can be used as a tool to identify new family members. For instance, reverse transcription-polymerase chain reaction (RT-PCR) can be used to amplify sequences encoding the conserved subtilisin-like catalytic domain from RNA obtained from a variety of tissue sources or cell lines. In particular, highly degenerate primers designed from the human PC4 sequences are useful for this purpose.

The present invention also provides polynucleotide molecules, including DNA and RNA molecules, that encode the human PC4 polypeptides disclosed herein. Those skilled in the art will readily recognize that, in view of the degeneracy of the genetic code, considerable sequence variation is possible among these polynucleotide molecules. SEQ ID NO:3 is a degenerate DNA sequence that encompasses all DNAs that encode the human PC4 polypeptide of SEQ ID NO:2. Those skilled in the art will recognize that the degenerate sequence of SEQ ID NO:3 also provides all RNA sequences encoding SEQ ID NO:2 by substituting U for T. Thus, human PC4 polypeptide-encoding polynucleotides comprising nucleotide 1 to nucleotide 2265 of SEQ ID NO:3 and their RNA equivalents are contemplated by the present invention. Table 1 sets forth the one-letter codes used within SEQ ID NO:3 to denote degenerate nucleotide positions. "Resolutions" are the nucleotides denoted by a code letter. "Complement" indicates the code for the complementary nucleotide(s). For example, the code Y denotes either C or T, and its complement R denotes A or G, A being complementary to T, and G being complementary to C.

                  TABLE 1                                                          ______________________________________                                         Nucleotide                                                                              Resolution   Nucleotide                                                                              Complement                                      ______________________________________                                         A        A            T        T                                               C        C            G        G                                               G        G            C        C                                               T        T            A        A                                               R        A|G Y        C|T                                    Y        C|T R        A|G                                    M        A|C K        G|T                                    K        G|T M        A|C                                    S        C|G S        C|G                                    W        A|T W        A|T                                    H        A|C|T                                                                     D        A|G|T                         B        C|G|T                                                                     V        A|C|G                         V        A|C|G                                                                     B        C|G|T                         D        A|G|T                                                                     H        A|C|T                         N        A|C|G|T                                                          N        A|C|G|T              ______________________________________                                    

The degenerate codons used in SEQ ID NO:3, encompassing all possible codons for a given amino acid, are set forth in Table 2.

                  TABLE 2                                                          ______________________________________                                                One                                                                     Amino  Letter                     Degenerate                                   Acid   Code    Codons             Codon                                        ______________________________________                                         Cys    C       TGC TGT            TGY                                          Ser    S       AGC AGT TCA TCC TCG TCT                                                                           WSN                                          Thr    T       ACA ACC ACG ACT    ACN                                          Pro    p       CCA CCC CCG CCT    CCN                                          Ala    A       GCA GCC GCG GCT    GCN                                          Gly    G       GGA GGC GGG GGT    GGN                                          Asn    N       AAC AAT            AAY                                          Asp    D       GAC GAT            GAY                                          Glu    E       GAA GAG            GAR                                          Gln    Q       CAA CAG            CAR                                          His    H       CAC CAT            CAY                                          Arg    R       AGA AGG CGA CGC CGG CGT                                                                           MGN                                          Lys    K       AAA AAG            AAR                                          Met    M       ATG                ATG                                          Ile    I       ATA ATC ATT        ATH                                          Leu    L       CTA CTC CTG CTT TTA TTG                                                                           YTN                                          Val    V       GTA GTC GTG GTT    GTN                                          Phe    F       TTC TTT            TTY                                          Tyr    Y       TAC TAT            TAY                                          Trp    W       TGG                TGG                                          Ter    .       TAA TAG TGA        TRR                                          Asn|Asp                                                                      B                          RAY                                          Glu|Gln                                                                      Z                          SAR                                          Any    X                          NNN                                          ______________________________________                                    

One of ordinary skill in the art will appreciate that some ambiguity is introduced in determining a degenerate codon, representative of all possible codons encoding each amino acid. For example, the degenerate codon for serine (WSN) can, in some circumstances, encode arginine (AGR), and the degenerate codon for arginine (MGN) can, in some circumstances, encode serine (AGY). A similar relationship exists between codons encoding phenylalanine and leucine. Thus, some polynucleotides encompassed by the degenerate sequence may encode variant amino acid sequences, but one of ordinary skill in the art can easily identify such variant sequences by reference to the amino acid sequence of SEQ ID NO:2. Variant sequences can be readily tested for functionality as described herein.

One of ordinary skill in the art will also appreciate that different species can exhibit "preferential codon usage." In general, see, Grantham, et al., Nuc. Acids Res. 8:1893-912, 1980; Haas, et al. Curr. Biol. 6:315-24, 1996; Wain-Hobson, et al., Gene 13:355-64, 1981; Grosjean and Fiers, Gene 18:199-209, 1982; Holm, Nuc. Acids Res. 14:3075-87, 1986; Ikemura, J. Mol. Biol. 158:573-97, 1982. As used herein, the term "preferential codon usage" or "preferential codons" is a term of art referring to protein translation codons that are most frequently used in cells of a certain species, thus favoring one or a few representatives of the possible codons encoding each amino acid (See Table 2). For example, the amino acid Threonine (Thr) may be encoded by ACA, ACC, ACG, or ACT, but in mammalian cells ACC is the most commonly used codon; in other species, for example, insect cells, yeast, viruses or bacteria, different Thr codons may be preferential. Preferential codons for a particular species can be introduced into the polynucleotides of the present invention by a variety of methods known in the art. Introduction of preferential codon sequences into recombinant DNA can, for example, enhance production of the protein by making protein translation more efficient within a particular cell type or species. Therefore, the degenerate codon sequence disclosed in SEQ ID NO:3 serves as a template for optimizing expression of polynucleotides in various cell types and species commonly used in the art and disclosed herein. Sequences containing preferential codons can be tested and optimized for expression in various species, and tested for functionality as disclosed herein.

Within preferred embodiments of the invention the isolated polynucleotides will hybridize to similar sized regions of SEQ ID NO:1, or a sequence complementary thereto, under stringent conditions. In general, stringent conditions are selected to be about 5° C. lower than the thermal melting point (T_(m)) for the specific sequence at a defined ionic strength and pH. The T_(m) is the temperature (under defined ionic strength and pH) at which 50% of the target sequence hybridizes to a perfectly matched probe. Typical stringent conditions are those in which the NaCl concentration is up to about 0.03 M at pH 7 and the temperature is at least about 60° C.

As previously noted, the isolated polynucleotides of the present invention include DNA and RNA. Methods for preparing DNA and RNA are well known in the art. In general, RNA is isolated from a tissue or cell that produces large amounts of human PC4 RNA. Such tissues and cells are identified by Northern blotting (Thomas, Proc. Nati. Acad. Sci. USA 77:5201, 1980), and include testis tissue, and testis-derived cell lines. Total RNA can be prepared using guanidine HCl extraction followed by isolation by centrifugation in a CsCl gradient (Chirgwin et al., Biochemistry 18:52-94, 1979). Poly (A)⁺ RNA is prepared from total RNA using the method of Aviv and Leder (Proc. Natl. Acad. Sci. USA 69:1408-12, 1972). Complementary DNA (cDNA) is prepared from poly(A)⁺ RNA using known methods. In the alternative, genomic DNA can be isolated. Polynucleotides encoding human PC4 polypeptides are then identified and isolated by, for example, hybridization or PCR.

A full-length clone encoding human PC4 can be obtained by conventional cloning procedures. Complementary DNA (cDNA) clones are preferred, although for some applications (e.g., expression in transgenic animals) it may be preferable to use a genomic clone, or to modify a cDNA clone to include at least one genomic intron. Methods for preparing cDNA and genomic clones are well known and within the level of ordinary skill in the art, and include the use of the sequence disclosed herein, or parts thereof, for probing or priming a library. Expression libraries can be probed with antibodies to human PC4, receptor fragments, or other specific binding partners. The present invention also provides for the isolation of human genomic sequences encoding a human prohormone convertase 4. Probes derived from SEQ ID NO: 1 can be used to screen genomic libraries from human sources to clone human genomic sequences of human PC4 according to standard procedures known in the art, and disclosed herein.

Those skilled in the art will recognize that the sequence disclosed in SEQ ID NO:1 represents a single allele of human PC4 and that allelic variation and alternative splicing are expected to occur. Allelic variants of this sequence can be cloned by probing cDNA or genomic libraries from different individuals according to standard procedures. Allelic variants of the DNA sequence shown in SEQ ID NO:1, including those containing silent mutations and those in which mutations result in amino acid sequence changes, are within the scope of the present invention, as are proteins which are allelic variants of SEQ ID NO:2. The present invention also provides for mRNA splice variant forms of the isolated polynucleotides that may occur naturally as a result of gene expression of human prohormone convertase 4. cDNAs generated from alternatively spliced mRNAs, which retain the properties of the human PC4 polypeptide are included within the scope of the present invention, as are polypeptides encoded by such cDNAs and mRNAs. Splice variants of this sequence can be cloned by probing human cDNA libraries, e.g. a human testicular cDNA library, according to standard procedures.

The present invention also provides isolated human prohormone convertase 4 polypeptides that are substantially homologous to the polypeptides of SEQ ID NO: 2 and their orthologs. In a preferred form, the isolated polypeptide is substantially free of other polypeptides, particularly other polypeptides of animal origin. It is preferred to provide the polypeptides in a highly purified form, i.e. greater than 95% pure, more preferably greater than 99% pure. The term "substantially homologous" is used herein to denote polypeptides having at least 85%, sequence identity to the sequences shown in SEQ ID NO: 2 or splice variants of SEQ ID NO:2. Such polypeptides will more preferably be at least 90% identical, and most preferably 95% or more identical to SEQ ID NO: 2 or splice variants of SEQ ID NO:2. Percent sequence identity is determined by conventional methods. see, for example, Altschul et al., Bull. Math. Bio. 48: 603-616, 1986 and Henikoff and Henikoff, Proc. Natl. Acad. Sci. USA 89:10915-10919, 1992. Briefly, two amino acid sequences are aligned to optimize the alignment scores using a gap opening penalty of 10, a gap extension penalty of 1, and the "blosum 62" scoring matrix of fienikoff and Henikoff (ibid.) as shown in Table 3 (amino acids are indicated by the standard one-letter codes).

                                      TABLE 3                                      __________________________________________________________________________     A   R N D C Q E G H I L K M F P S T W Y V                                      __________________________________________________________________________     A   4                                                                          R -1                                                                                 5                                                                        N -2                                                                                 0                                                                                6                                                                      D -2                                                                               -2                                                                                 1                                                                                6                                                                    C   0                                                                              -3                                                                               -3                                                                               -3                                                                                 9                                                                  Q -1                                                                                 1                                                                                0                                                                                0                                                                              -3                                                                                 5                                                                E -1                                                                                 0                                                                                0                                                                                2                                                                              -4                                                                                 2                                                                                5                                                              G   0                                                                              -2                                                                                 0                                                                              -1                                                                               -3                                                                               -2                                                                               -2                                                                                 6                                                            H -2                                                                                 0                                                                                1                                                                              -1                                                                               -3                                                                                 0                                                                                0                                                                              -2                                                                                 8                                                          I -1                                                                               -3                                                                               -3                                                                               -3                                                                               -1                                                                               -3                                                                               -3                                                                               -4                                                                               -3                                                                                 4                                                        L -1                                                                               -2                                                                               -3                                                                               -4                                                                               -1                                                                               -2                                                                               -3                                                                               -4                                                                               -3                                                                                 2                                                                                4                                                      K -1                                                                                 2                                                                                0                                                                              -1                                                                               -3                                                                                 1                                                                                1                                                                              -2                                                                               -1                                                                               -3                                                                               -2                                                                                 5                                                    M -1                                                                               -1                                                                               -2                                                                               -3                                                                               -1                                                                                 0                                                                              -2                                                                               -3                                                                               -2                                                                                 1                                                                                2                                                                              -1                                                                                 5                                                  F -2                                                                               -3                                                                               -3                                                                               -3                                                                               -2                                                                               -3                                                                               -3                                                                               -3                                                                               -1                                                                                 0                                                                                0                                                                              -3                                                                                 0                                                                                6                                                P -1                                                                               -2                                                                               -2                                                                               -1                                                                               -3                                                                               -1                                                                               -1                                                                               -2                                                                               -2                                                                               -3                                                                               -3                                                                               -1                                                                               -2                                                                               -4                                                                                 7                                              S   1                                                                              -1                                                                                 1                                                                                0                                                                              -1                                                                                 0                                                                                0                                                                                0                                                                              -1                                                                               -2                                                                               -2                                                                                 0                                                                              -1                                                                               -2                                                                               -1                                                                                 4                                            T   0                                                                              -1                                                                                 0                                                                              -1                                                                               -1                                                                               -1                                                                               -1                                                                               -2                                                                               -2                                                                               -1                                                                               -1                                                                               -1                                                                               -1                                                                               -2                                                                               -1                                                                                 1                                                                                5                                          W -3                                                                               -3                                                                               -4                                                                               -4                                                                               -2                                                                               -2                                                                               -3                                                                               -2                                                                               -2                                                                               -3                                                                               -2                                                                               -3                                                                               -1                                                                                 1                                                                              -4                                                                               -3                                                                               -2                                                                               11                                         Y -2                                                                               -2                                                                               -2                                                                               -3                                                                               -2                                                                               -1                                                                               -2                                                                               -3                                                                                 2                                                                              -1                                                                               -1                                                                               -2                                                                               -1                                                                                 3                                                                              -3                                                                               -2                                                                               -2                                                                                 2    7                                   V   0                                                                              -3                                                                               -3                                                                               -3                                                                               -1                                                                               -2                                                                               -2                                                                               -3                                                                               -3                                                                                 3                                                                                1                                                                              -2                                                                                 1                                                                              -1                                                                               -2                                                                               -2                                                                                 0                                                                              -3   -1                                                                          4                                        __________________________________________________________________________

The percent identity of the optimal alignment is calculated as: ##EQU1##

Sequence identity of polynucleotide molecules is determined by similar methods using a ratio as disclosed above.

Variant human PC4 polypeptides or substantially homologous human PC4 polypeptides are characterized as having one or more amino acid substitutions, deletions or additions. These changes are preferably of a minor nature, that is conservative amino acid substitutions (see Table 4) and other substitutions that do not significantly affect the folding or activity of the polypeptide; small deletions, typically of one to about 30 amino acids; and small amino- or carboxyl-terminal extensions, such as an amino-terminal methionine residue, a small linker peptide of up to about 20-25 residues, or an affinity tag, such as a small extension that facilitates purification, such as a poly-histidine tract, an antigenic epitope or a binding domain. See, in general Ford et al., Protein Expression and Purification 2: 95-107, 1991. Polypeptides comprising affinity tags can further comprise a proteolytic cleavage site between the human PC4 polypeptide and the affinity tag. Such cleavage sites include, for example, thrombin cleavage sites and factor Xa cleavage sites.

                  TABLE 4                                                          ______________________________________                                         Conservative amino acid substitutions                                          ______________________________________                                         Basic:              arginine                                                                       lysine                                                                         histidine                                                  Acidic:             glutamic acid                                                                  aspartic acid                                              Polar:              glutamine                                                                      asparagine                                                 Hydrophobic:        leucine                                                                        isoleucine                                                                     valine                                                     Aromatic:           phenylalanine                                                                  tryptophan                                                                     tyrosine                                                   Small:              glycine                                                                        alanine                                                                        serine                                                                         threonine                                                                      methionine                                                 ______________________________________                                    

The proteins of the present invention can also comprise non-naturally occurring amino acid residues. Non-naturally occurring amino acids include, without limitation, trans-3-methylproline, 2,4-methanoproline, cis-4-hydroxyproline, trans-4-hydroxyproline, N-methylglycine, allo-threonine, methylthreonine, hydroxyethylcysteine, hydroxyethylhomocysteine, nitroglutamine, homoglutamine, pipecolic acid, thiazolidine carboxylic acid, dehydroproline, 3- and 4-methylproline, 3,3-dimethylproline, tert-leucine, norvaline, 2-azaphenylalanine, 3- azaphenylalanine, 4-azaphenylalanine, and 4-fluorophenylalanine. Several methods are known in the art for incorporating non-naturally occurring amino acid residues into proteins. For example, an in vitro system can be employed wherein nonsense mutations are suppressed using chemically aminoacylated suppressor tRNAs. Methods for synthesizing amino acids and aminoacylating tRNA are known in the art. Transcription and translation of plasmids containing nonsense mutations is carried out in a cell-free system comprising an E. coli S30 extract and commercially available enzymes and other reagents. Proteins are purified by chromatography. See, for example, Robertson et al., J. Am. Chem. Soc. 113:2722, 1991; Ellman et al., Methods Enzymol. 202:301, 1991; Chung et al., Science 259:806-9, 1993; and Chung et al., Proc. Natl. Acad. Sci. USA 90:10145-9, 1993). In a second method, translation is carried out in Xenopus oocytes by microinjection of mutated mRNA and chemically aminoacylated suppressor tRNAs (Turcatti et al., J. Biol. Chem. 271:19991-8, 1996). Within a third method, E. coli cells are cultured in the absence of a natural amino acid that is to be replaced (e.g., phenylalanine) and in the presence of the desired non-naturally occurring amino acid(s) (e.g., 2-azaphenylalanine, 3-azaphenylalanine, 4-azaphenylalanine, or 4-fluorophenylalanine). The non-naturally occurring amino acid is incorporated into the protein in place of its natural counterpart. See, Koide et al., Biochem. 33:7470-6, 1994. Naturally occurring amino acid residues can be converted to non-naturally occurring species by in vitro chemical modification. Chemical modification can be combined with site-directed mutagenesis to further expand the range of substitutions (Wynn and Richards, Protein Sci. 2:395-403, 1993).

A limited number of non-conservative amino acids, amino acids that are not encoded by the genetic code, non-naturally occurring amino acids, and unnatural amino acids may be substituted for human PC4 amino acid residues.

Essential amino acids in the polypeptides of the present invention can be identified according to procedures known in the art, such as site-directed mutagenesis or alanine-scanning mutagenesis (Cunningham and Wells, Science 244, 1081-1085, 1989; Bass et al., Proc. Natl. Acad. Sci. USA 88:4498-502, 1991). In the latter technique, single alanine mutations are introduced at every residue in the molecule, and the resultant mutant molecules are tested for biological activity, as disclosed below, to identify amino acid residues that are critical to the activity of the molecule. See also, Hilton et al., J. Biol. Chem. 271:4699-708, 1996. Sites of human PC4 15 catalytic domain important for interaction with its substrate(s) can also be determined by physical analysis of structure, as determined by such techniques as nuclear magnetic resonance, crystallography, electron diffraction or photoaffinity labeling, in conjunction with mutation of putative contact site amino acids. See, for example, de Vos et al., Science 255:306-12, 1992; Smith et al., J. Mol. Biol. 224:899-904, 1992; Wlodaver et al., FEBS Lett. 309:59-64, 1992. The identities of essential amino acids can also be inferred, by one of skill in the art, from analysis of homologies with related prohormone convertases.

Multiple amino acid substitutions can be made and tested using known methods of mutagenesis and screening, such as those disclosed by Reidhaar-Olson and Sauer (Science 241:53-57, 1988) or Bowie and Sauer (Proc. Natl. Acad. Sci. USA 86:2152-2156, 1989). Briefly, these authors disclose methods for simultaneously randomizing two or more positions in a polypeptide, selecting for functional polypeptide, and then sequencing the mutagenized polypeptides to determine the spectrum of allowable substitutions at each position. Other methods that can be used include phage display (e.g., Lowman et al., Biochem. 30:10832-10837, 1991; Ladner et al., U.S. Pat. No. 5,223,409; Huse, WIPO Publication WO 92/06204) and region-directed mutagenesis (Derbyshire et al., Gene 46:145, 1986; Ner et al., DNA 7:127, 1988).

Variants of the disclosed human PC4 DNA and polypeptide sequences can be generated through DNA shuffling as disclosed by Stemmer, Nature 370:389-91, 1994; Stemmer, Proc. Natl. Acad. Sci. USA 91:10747-51, 1994; and WIPO Publication WO 97/20078. Briefly, variant DNAs are generated by in vitro homologous recombination by random fragmentation of a parent DNA followed by reassembly using PCR, resulting in randomly introduced point mutations. This technique can be modified by using a family of parent DNAs, such as allelic variants or DNAs from different species, to introduce additional variability into the process. Selection or screening for the desired activity, followed by additional iterations of mutagenesis and assay provides for rapid "evolution" of sequences by selecting for desirable mutations while simultaneously selecting against detrimental changes.

Mutagenesis methods as disclosed herein can be combined with high-throughput, automated screening methods to detect activity of cloned, mutagenized polypeptides in host cells. Mutagenized DNA molecules that encode active polypeptides (e.g., cleave a known indicator polypeptide substrate) can be recovered from the host cells and rapidly sequenced using modern equipment. These methods allow the rapid determination of the importance of individual amino acid residues in a polypeptide of interest, and can be applied to polypeptides of unknown structure. Moreover, these mutagenesis methods can be used to engineer proteins that alter reaction kinetics, constrict or expand the substrate specificity, or alter tissue and cellular localization of a polypeptide, such as human prohormone convertase 4.

Using the methods discussed above, one of ordinary skill in the art can prepare a variety of polypeptides that are substantially homologous to residues 1 to 755 of SEQ ID NO: 2 or allelic variants or splice variants thereof and retain the activity of the wild-type protein.

Moreover, using methods described in the art, polypeptide fusions, or hybrid prohormone convertase proteins, are constructed using regions or domains of the inventive human prohormone convertase 4 in combination with those of other known or unknown prohormone convertase proteins (e.g. PC2 and PC1), or heterologous proteins (Sambrook et al., ibid., Altschul et al., ibid., Picard, D., Cur. Opin. Biology 5:511-515, 1994, and references therein). These methods allow the determination of the biological importance of larger domains or regions in a polypeptide of interest. Such hybrids alter reaction kinetics, constrict or expand the substrate specificity, or alter tissue and cellular localization of a polypeptide, and can be applied to polypeptides of unknown structure.

Fusion proteins can be prepared by methods known to those skilled in the art. A polynucleotide encoding each component of the fusion protein in the proper reading frame can be generated using known techniques and expressed by the methods described herein. For example, part or all of a domain conferring biological function may be swapped between the human PC4 of the present invention with the corresponding domain from another prohormone convertase, such as PC2 or PC1. Such domains comprise but are not limited to the secretory signal sequence, Homo-A domain, catalytic domain, Homo-B domain, and C-terminal portion of the molecule described herein. One or several domains, such as those described above, can be swapped in this fashion by linking polynucleotide segments in the proper reading frame, creating a DNA polysegment encoding the several domains of the fusion protein. Methods to make such fusion proteins are well known in the art (Sambrook et al., ibid., Altschul et al., ibid., Picard, D., ibid.). Such fusion proteins contain at least one domain from human PC4, and would be expected to have a biological functional profile that is the same or similar to polypeptides of the present invention or other known or unknown prohormone convertase proteins (e.g. PC2 and PC1), depending on the fusion constructed. Moreover, such fusion proteins may exhibit other properties as disclosed above.

For any human PC4 polypeptide, including variants and fusion proteins, one of ordinary skill in the art can readily generate a fully degenerate polynucleotide sequence encoding that variant using the information disclosed herein and set forth in Tables 1 and 2 above.

The polypeptides of the present invention, including full-length polypeptides, biologically active fragments, and fusion polypeptides, can be produced in genetically engineered host cells according to conventional techniques. Suitable host cells are those cell types that can be transformed or transfected with exogenous DNA and grown in culture, and include bacteria, fungal cells, and cultured higher eukaryotic cells. Eukaryotic cells, particularly cultured cells of multicellular organisms, are preferred. Techniques for manipulating cloned DNA molecules and introducing exogenous DNA into a variety of host cells are disclosed by Sambrook et al., Molecular Cloning: A Laboratory Manual, 2nd ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989, and Ausubel et al., eds., Current Protocols in Molecular Biology, John Wiley and Sons, Inc., NY, 1987.

In general, a DNA sequence encoding a human prohormone convertase 4 polypeptide is operably linked to other genetic elements required for its expression, generally including a transcription promoter and terminator, within an expression vector. The vector will also commonly contain one or more selectable markers and one or more origins of replication, although those skilled in the art will recognize that within certain systems selectable markers may be provided on separate vectors, and replication of the exogenous DNA may be provided by integration into the host cell genome. Selection of promoters, terminators, selectable markers, vectors and other elements is a matter of routine design within the level of ordinary skill in the art. Many such elements are described in the literature and are available through commercial suppliers.

To direct a human prohormone convertase 4 polypeptide into the secretory pathway of a host cell, a secretory signal sequence (also known as a leader sequence, prepro sequence or pre sequence) is provided in the expression vector. The secretory signal sequence may be that of the human prohormone convertase 4 polypeptide, or may be derived from another protein targeted to the secretory pathway (e.g., t-PA) or synthesized de novo. The secretory signal sequence is joined to the human prohormone convertase 4 DNA sequence in the correct reading frame and positioned to direct the newly synthesized polypeptide into the secretory pathway of the host cell. Secretory signal sequences are commonly positioned 5' to the DNA sequence encoding the polypeptide of interest, although certain secretory signal sequences may be positioned elsewhere in the DNA sequence of interest (see, e.g., Welch et al., U.S. Pat. No. 5,037,743; Holland et al., U.S. Pat. No. 5,143,830).

Alternatively, the secretory signal sequence contained in the polypeptides of the present invention can be used to direct other polypeptides into the secretory pathway. The present invention provides for such fusion polypeptides. A signal fusion polypeptide can be made wherein a secretory signal sequence encoding amino acid residue 1 (Met) to residue 19 (Val) of SEQ ID NO:2 is operably linked to a DNA segment encoding another polypeptide using methods known in the art and disclosed herein. The secretory peptide contained in the resulting fusion polypeptides of the present invention is preferably fused amino-terminally to an additional peptide to direct the additional peptide into the secretory pathway. Such constructs have numerous applications known in the art. For example, these novel secretory signal sequence fusion constructs can direct, for example, the secretion of an active component of a protein not normally fully-secreted, such as a cell-surface receptor, or another non-secreted protein. Such fusions may be used in vivo or in vitro to direct peptides through the secretory pathway.

Cultured mammalian cells are suitable hosts within the present invention. Methods for introducing exogenous DNA into mammalian host cells include calcium phosphate-mediated transfection (Wigler et al., Cell 14:725, 1978; Corsaro and Pearson, Somatic Cell Genetics 7:603, 1981: Graham and Van der Eb, Virology 52:456, 1973), electroporation (Neumann et al., EMBO J. 1:841-845, 1982), DEAE-dextran mediated transfection (Ausubel et al., ibid.), and liposome-mediated transfection (Hawley-Nelson et al., Focus 15:73, 1993; Ciccarone et al., Focus 15:80, 1993, and viral vectors (Miller and Rosman, BioTechniques 7:980-90, 1989; Wang and Finer, Nature Med. 2:714-6, 1996). The production of recombinant polypeptides in cultured mammalian cells is disclosed, for example, by Levinson et al., U.S. Pat. No. 4,713,339; Hagen et al., U.S. Pat. No. 4,784,950; Palmiter et al., U.S. Pat. No. 4,579,821; and Ringold, U.S. Pat. No. 4,656,134. Suitable cultured mammalian cells include the COS-1 (ATCC No. CRL 1650), COS-7 (ATCC No. CRL 1651), BHK (ATCC No. CRL 1632), BHK 570 (ATCC No. CRL 10314), 293 (ATCC No. CRL 1573; Graham et al., J. Gen. Virol. 36:59-72, 1977) and Chinese hamster ovary (e.g. CHO-Ki; ATCC No. CCL 61) cell lines. Other preferred cell lines are cultured testicular cells including dolphin DBl.Tes cells (CRL-6258); mouse GC-1 spg cells (CRL-2053); TM3 cells (CRL-1714); TM4 cells (CRL-1715); and pig ST cells (CRL-1746), available from American Type Culture Collection, Rockville, Md. Additional suitable cell lines are known in the art and available from public depositories such as the American Type Culture Collection, Rockville, Md. In general, strong transcription promoters are preferred, such as promoters from SV-40 or cytomegalovirus. See, e.g., U.S. Pat. No. 4,956,288. Other suitable promoters include those from metallothionein genes (U.S. Pat. Nos. 4,579,821 and 4,601,978) and the adenovirus major late promoter.

Drug selection is generally used to select for cultured mammalian cells into which foreign DNA has been inserted. Such cells are commonly referred to as "transfectants". Cells that have been cultured in the presence of the selective agent and are able to pass the gene of interest to their progeny are referred to as "stable transfectants." A preferred selectable marker is a gene encoding resistance to the antibiotic neomycin. Selection is carried out in the presence of a neomycin-type drug, such as G-418 or the like. Selection systems can also be used to increase the expression level of the gene of interest, a process referred to as "amplification." Amplification is carried out by culturing transfectants in the presence of a low level of the selective agent and then increasing the amount of selective agent to select for cells that produce high levels of the products of the introduced genes. A preferred amplifiable selectable marker is dihydrofolate reductase, which confers resistance to methotrexate. Other drug resistance genes (e.g. hygromycin resistance, multi-drug resistance, puromycin acetyltransferase) can also be used. Alternative markers that introduce an altered phenotype, such as green fluorescent protein, or cell surface proteins such as CD4, CD8, Class I MHC, placental alkaline phosphatase may be used to sort transfected cells from untransfected cells by such means as FACS sorting or magnetic bead separation technology.

Other higher eukaryotic cells can also be used as hosts, including plant cells, insect cells and avian cells. The use of Agrobacterium rhizogenes as a vector for expressing genes in plant cells has been reviewed by Sinkar et al., J. Biosci. (Bangalore) 11:47-58, 1987. Transformation of insect cells and production of foreign polypeptides therein is disclosed by Guarino et al., U.S. Pat. No. 5,162,222 and WIPO publication WO 94/06463. Insect cells can be infected with recombinant baculovirus, commonly derived from Autographa californica nuclear polyhedrosis virus (AcNPV). See, King, L. A. and Possee, R. D., The Baculovirus Expression System: A Laboratory Guide, London, Chapman & Hall; O'Reilly, D. R. et al., Baculovirus Expression Vectors: A Laboratory Manual, New York, Oxford University Press., 1994; and, Richardson, C.

D., Ed., Baculovirus Expression Protocols. Methods in Molecular Biology, Totowa, N.J., Humana Press, 1995. A second method of making recombinant human PC4 baculovirus utilizes a transposon-based system described by Luckow (Luckow, V. A, et al., J Virol 67:4566-79, 1993). This system, which utilizes transfer vectors, is sold in the Bac-to-Bac™ kit (Life Technologies, Rockville, Md.). See, Hill-Perkins, M. S. and Possee, R. D., J Gen Virol 71:971-6, 1990; Bonning, B. C. et al., J Gen Virol 75:1551-6, 1994; and, Chazenbalk, G. D., and Rapoport, B., J Biol Chem 270:1543-9, 1995. In addition, transfer vectors can include an in-frame fusion with DNA encoding an epitope tag at the C- or N-terminus of the expressed human PC4 polypeptide, for example, a Glu--Glu epitope tag (Grussenmeyer, T. et al., Proc. Natl. Acad. Sci. 82:7952-4, 1985). Using a technique known in the art, a transfer vector containing human PC4 is transformed into E. Coli, and screened for bacmids which contain an interrupted lacZ gene indicative of recombinant baculovirus. The bacmid DNA containing the recombinant baculovirus genome is isolated, using common techniques, and used to transfect Spodoptera frugiperda cells, e.g. Sf9 cells. Recombinant virus that expresses human PC4 is subsequently produced. Recombinant viral stocks are made by methods commonly used the art.

The recombinant virus is used to infect host cells, typically a cell line derived from the fall armyworm, Spodoptera frugiperda. See, in general, Glick and Pasternak, Molecular Biotechnology: Principles and Applications of Recombinant DNA, ASM Press, Washington, D.C., 1994. Another suitable cell line is the High FiveO™ cell line (Invitrogen) derived from Trichoplusia ni (U.S. Pat. No. 5,300,435). Commercially available serum-free media are used to grow and maintain the cells. Suitable media are Sf900 II™ (Life Technologies) or ESF ₉₂₁ ™ (Expression Systems) for the Sf9 cells; and Ex-cellO405™ (JRH Biosciences, Lenexa, Kans.) or Express FiveO™ (Life Technologies) for the T. ni cells. The cells are grown up from an inoculation density of approximately 2-5×10⁵ cells to a density of 1-2×10⁶ cells at which time a recombinant viral stock is added at a multiplicity of infection (MOI) of 0.1 to 10, more typically near 3. Procedures used are generally described in available laboratory manuals (King, L. A. and Possee, R. D., ibid.; O'Reilly, D .R. et al., ibid.; Richardson, C. D., ibid.). Subsequent purification of the human PC4 polypeptide from the supernatant can be achieved using methods described herein.

Fungal cells, including yeast cells, can also be used within the present invention. Yeast species of particular interest in this regard include Saccharomyces cerevisiae, Pichia pastoris, and Pichia methanolica. Methods for transforming S. cerevisiae cells with exogenous DNA and producing recombinant polypeptides therefrom are disclosed by, for example, Kawasaki, U.S. Pat. No. 4,599,311; Kawasaki et al., U.S. Pat. No. 4,931,373; Brake, U.S. Pat. No. 4,870,008; Welch et al., U.S. Pat. No. 5,037,743; and Murray et al., U.S. Pat. No. 4,845,075. Transformed cells are selected by phenotype determined by the selectable marker, commonly drug resistance or the ability to grow in the absence of a particular nutrient (e.g., leucine). A preferred vector system for use in Saccharomyces cerevisiae is the POT1 vector system disclosed by Kawasaki et al. (U.S. Pat. No. 4,931,373), which allows transformed cells to be selected by growth in glucose-containing media. Suitable promoters and terminators for use in yeast include those from glycolytic enzyme genes (see, e.g., Kawasaki, U.S. Pat. No. 4,599,311; Kingsman et al., U.S. Pat. No. 4,615,974; and Bitter, U.S. Pat. No. 4,977,092) and alcohol dehydrogenase genes. See also U.S. Pat. Nos. 4,990,446; 5,063,154; 5,139,936 and 4,661,454. Transformation systems for other yeasts, including Hansenula polymorpha, Schizosaccharomyces pombe, Kluyveromyces lactis, Kluyveromiyces fragilis, Ustilago maydis, Pichia pastoris, Pichia methanolica, Pichia guillermondii and Candida maltosa are known in the art. See, for example, Gleeson et al., J. Gen. Microbiol. 132:3459-3465, 1986 and Cregg, U.S. Pat. No. 4,882,279. Aspergillus cells may be utilized according to the methods of McKnight et al., U.S. Pat. No. 4,935,349. Methods for transforming Acremonium chrysogenum are disclosed by Sumino et al., U.S. Pat. No. 5,162,228. Methods for transforming Neurospora are disclosed by Lambowitz, U.S. Pat. No. 4,486,533.

The use of Pichia methanolica as host for the production of recombinant proteins is disclosed in WIPO Publications WO 97/17450, WO 97/17451, WO 98/02536, and WO 98/02565. DNA molecules for use in transforming P. methanolica will commonly be prepared as double-stranded, circular plasmids, which are preferably linearized prior to transformation. For polypeptide production in P. methanolica, it is preferred that the promoter and terminator in the plasmid be that of a P. methanolica gene, such as a P. methanolica alcohol utilization gene (AUG1 or AUG2). Other useful promoters include those of the dihydroxyacetone synthase (DHAS), formate dehydrogenase (FMD), and catalase (CAT) genes. To facilitate integration of the DNA into the host chromosome, it is preferred to have the entire expression segment of the plasmid flanked at both: ends by host DNA sequences. A preferred selectable marker for use in Pichia methanolica is a P. methanolica ADE2 gene, which encodes phosphoribosyl-5-aminoimidazole carboxylase (AIRC; EC 4.1.1.21), which allows ade2 host cells to grow in the absence of adenine. For large-scale, industrial processes where it is desirable to minimize the use of methanol, it is preferred to use host cells in which both methanol utilization genes (AUG1 and AUG2) are deleted. For production of secreted proteins, host cells deficient in vacuolar protease genes (PEP4 and PRBI) are preferred. Electroporation is used to facilitate the introduction of a plasmid containing DNA encoding a polypeptide of interest into P. methanolica cells. It is preferred to transform P. methanolica cells by electroporation using an exponentially decaying, pulsed electric field having a field strength of from 2.5 to 4.5 kV/cm, preferably about 3.75 kV/cm, and a time constant (t) of from 1 to 40 milliseconds, most preferably about 20 milliseconds. P. methanolica cells are cultured in a medium comprising adequate sources of carbon, nitrogen and trace nutrients at a temperature of about 25° C. to 35° C. Liquid cultures are provided with sufficient aeration by conventional means, such as shaking of small flasks or sparging of fermentors. A preferred culture medium for P. methanolica is YEPD (2% D-glucose, 2% Bacto™ Peptone (Difco Laboratories, Detroit, MI), 1% BactoTM yeast extract (Difco Laboratories), 0.004% adenine and 0.006% L-leucine).

Prokaryotic host cells, including strains of the bacteria Escherichia coli, Bacillus and other genera are also useful host cells within the present invention. Techniques for transforming these hosts and expressing foreign DNA sequences cloned therein are well known in the art (see, e.g., Sambrook et al., ibid.). When expressing a human PC4 polypeptide in bacteria such as E. coli, the polypeptide may be retained in the cytoplasm, typically as insoluble granules, or may be directed to the periplasmic space by a bacterial secretion sequence. In the former case, the cells are lysed, and the granules are recovered and denatured using, for example, guanidine isothiocyanate or urea. The denatured polypeptide can then be refolded and dimerized by diluting the denaturant, such as by dialysis against a solution of urea and a combination of reduced and oxidized glutathione, followed by dialysis against a buffered saline solution. In the latter case, the polypeptide can be recovered from the periplasmic space in a soluble and functional form by disrupting the cells (by, for example, sonication or osmotic shock) to release the contents of the periplasmic space and recovering the protein, thereby obviating the need for denaturation and refolding.

Transformed or transfected host cells are cultured according to conventional procedures in a culture medium containing nutrients and other components required for the growth of the chosen host cells. A variety of suitable media, including defined media and complex media, are known in the art and generally include a carbon source, a nitrogen source, essential amino acids, vitamins and minerals. Media may also contain such components as growth factors or serum, as required. The growth medium will generally select for cells containing the exogenously added DNA by, for example, drug selection or deficiency in an essential nutrient which is complemented by the selectable marker carried on the expression vector or co-transfected into the host cell.

It is preferred to purify the polypeptides of the present invention to ≧80% purity, more preferably to ≧90% purity, even more preferably ≧95% purity, and particularly preferred is a pharmaceutically pure state, that is greater than 99.9% pure with respect to contaminating macromolecules, particularly other proteins and nucleic acids, and free of infectious and pyrogenic agents. Preferably, a purified polypeptide is substantially free of other polypeptides, particularly other polypeptides of animal origin.

Human prohormone convertase 4 polypeptides prepared according to the present invention are purified using methods generally known in the art, such as affinity purification and separations based on size, charge, solubility and other properties of the protein. When the protein is produced in cultured mammalian cells, it is preferred to culture the cells in a serum-free culture medium in order to limit the amount of contaminating protein. The cells are harvested, lysed and fractionated. Preferred methods of fractionation include affinity chromatography, Q-Fast Flow Sepharose, MonoQ resin, FPLC, phenyl Sepharose, hydroxyapatite, MonoS and/or S-Sepharose. Proteins can also be purified using an immobilized affinity tag (e.g., polyhistidine, substance P or other polypeptide or protein for which an antibody or other specific binding agent is available). A specific cleavage site may be provided between the protein of interest and the affinity tag. Preferred affinity tags include, for example, a polyhistidine tail, which permits purification of the fusion protein on immobilized nickel (Houchuli et al., Bio/Technol. 6:1321-1325, 1988). Truncated forms of the polypeptide, e.g. lacking transmembrane or secretory signal sequence domains, may also be constructed and used to more readily purify catalytically active prohormone convertases (Nakayama, K. Methods in Enz., 244: 167-175, 1995). In prokaryotic expression systems, a maltose binding protein (MBP) fusion may be advantageously used as an affinity tag. If the protein is to be recovered from the cytoplasm or periplasm of the host cells, the cells are first disrupted, and a crude extract containing the protein is recovered and subjected to further purification steps. Moreover, human prohormone polypeptide substrates and their cleavage products resulting from cleavage by the present invention are purified using methods generally known in the art as disclosed above, with minor changes. For example, secreted proteins, such as cleavage products, are recovered from cell-conditioned media, preferably after concentration of the conditioned media. Selection of particular fractionation steps and the sequence of those steps will be based in part of the type of host cell and the expression system chosen. Such determinations are within the level of ordinary skill in the art. Selection of a particular method is a matter of routine design and is determined in part by the properties of the chosen support. See, for example, Affinity Chromatography: Principles & Methods, Pharmacia LKB Biotechnology, Uppsala, Sweden, 1988.

The polypeptides of the present invention can be isolated by exploitation of their structural and biochemical properties. For example, immobilized metal ion adsorption (IMAC) chromatography can be used to purify histidine-rich proteins, including those comprising polyhistidine tags. Briefly, a gel is first charged with divalent metal ions to form a chelate (Sulkowski, Trends in Biochem. 3:1-7, 1985). Histidine-rich proteins will be adsorbed to this matrix with differing affinities, depending upon the metal ion used, and will be eluted by competitive elution, lowering the pH, or use of strong chelating agents. Other methods of purification include purification of glycosylated proteins by lectin affinity chromatography and ion exchange chromatography (Methods in Enzymol., Vol. 182, "Guide to Protein Purification", M.

Deutscher, (ed.), Acad. Press, San Diego, 1990, pp.529-39). Within additional embodiments of the invention, a fusion of the polypeptide of interest and an affinity tag (e.g., maltose-binding protein, an immunoglobulin domain) may be constructed to facilitate purification.

Human PC4 polypeptides can also be used to prepare antibodies that specifically bind to human PC4 epitopes, peptides or polypeptides. The human PC4 polypeptide or a fragment thereof serves as an antigen (immunogen) to inoculate an animal and elicit an immune response. Suitable antigens include the various human PC4 polypeptide domains disclosed herein encoded within SEQ ID NO:2, or a contiguous 9 to 755 amino acid fragment encoded within SEQ ID NO:2. Polyclonal and Monoclonal antibodies generated from this immune response are isolated and purified using methods that are well known in the art. See, for example, Current Protocols in Immunology, Cooligan, et al. (eds.), National Institutes of Health, John Wiley and Sons, Inc., 1995; Sambrook et al., Molecular Cloning: A Laboratory Manual, Second Edition, Cold Spring Harbor, N.Y., 1989; and Hurrell, J. G. R., Ed., Monoclonal Hybridoma Antibodies: Techniques and Applications, CRC Press, Inc., Boca Raton, Fla., 1982.

As would be evident to one of ordinary skill in the art, polyclonal antibodies can be generated from inoculating a variety of warm-blooded animals such as horses, cows, goats, sheep, dogs, chickens, rabbits, mice, and rats, with a human PC4 polypeptide or a fragment thereof. The immunogenicity of a human prohormone convertase 4 polypeptide may be increased through the use of an adjuvant, such as alum (aluminum hydroxide) or Freund's complete or incomplete adjuvant. Polypeptides useful for immunization also include fusion polypeptides, such as fusions of human prohormone convertase 4 or a portion thereof with an immunoglobulin polypeptide or with maltose binding protein. The polypeptide immunogen may be a full-length molecule or a portion thereof. If the polypeptide portion is "hapten-like", such portion may be advantageously joined or linked to a macromolecular carrier (such as keyhole limpet hemocyanin (KLH), bovine serum albumin (BSA) or tetanus toxoid) for immunization.

As used herein, the term "antibodies" includes polyclonal antibodies, affinity-purified polyclonal antibodies, monoclonal antibodies, and antigen-binding fragments, such as F(ab')₂ and Fab' proteolytic fragments. Genetically engineered intact antibodies or fragments, such as chimeric antibodies, Fv fragments, single chain antibodies and the like, as well as synthetic antigen-binding peptides and polypeptides, are also included. Non-human antibodies may be humanized by grafting non-human CDRs onto human framework and constant regions, or by incorporating the entire non-human variable domains (optionally "cloaking" them with a human-like surface by replacement of exposed residues, wherein the result is a "veneered" antibody). In some instances, humanized antibodies may retain non-human residues within the human variable region framework domains to enhance proper binding characteristics. Through humanizing antibodies, biological half-life may be increased, and the potential for adverse immune reactions upon administration to humans is reduced.

Alternative techniques for generating or selecting antibodies useful herein include in vitro exposure of lymphocytes to human prohormone convertase 4 protein or a peptide therefrom, and selection of antibody display libraries in phage or similar vectors (for instance, through use of immobilized or labeled human PC4 protein or peptide). Genes encoding polypeptides having potential human PC4 polypeptide binding domains can be obtained by screening random peptide libraries displayed on phage (phage display) or on bacteria, such as E. coli. Nucleotide sequences encoding the polypeptides can be obtained in a number of ways, such as through random mutagenesis and random polynucleotide synthesis. These random peptide display libraries can be used to screen for peptides which interact with a known target which can be a protein or polypeptide, such as a ligand or receptor, a biological or synthetic macromolecule, or organic or inorganic substances. Techniques for creating and screening such random peptide display libraries are known in the art (Ladner et al., U.S. Pat. No. 5,223,409; Ladner et al., U.S. Pat. No. 4,946,778; Ladner et al., US Patent NO. 5,403,484 and Ladner et al., U.S. Pat. No. 5,571,698) and random peptide display libraries and kits for screening such libraries are available commercially, for instance from Clontech (Palo Alto, Calif.), Invitrogen Inc. (San Diego, Calif.), New England Biolabs, Inc. (Beverly, Mass.) and Pharmacia LKB Biotechnology Inc. (Piscataway, N.J.). Random peptide display libraries can be screened using the human PC4 sequences disclosed herein to identify proteins which bind to human PC4. These "binding proteins" which interact with human PC4 polypeptides can be used for tagging cells; for isolating homolog polypeptides by affinity purification; they can be directly or indirectly conjugated to drugs, toxins, radionuclides and the like. These binding proteins can also be used in analytical methods such as for screening expression libraries and neutralizing activity. The binding proteins can also be used for diagnostic assays for determining levels of polypeptides in tissues; for detecting or quantitating polypeptides as marker of underlying pathology or disease.

These binding proteins can also act as human PC4 "antagonists" to block human PC4 cleavage activity in vitro and in vivo.

Antibodies are determined to be specifically binding if: 1) they exhibit a threshold level of binding activity, and 2) they do not significantly cross-react with related polypeptide molecules. First, antibodies herein specifically bind if they bind if they bind to a human prohormone convertase 4 polypeptide, peptide or epitope with an affinity at least 10-fold greater than the binding affinity to control (non-human PC4) polypeptide. It is preferred that the antibodies exhibit a binding affinity (Ka) of 10⁶ M⁻¹ or greater, preferably 10⁷ M⁻¹ or greater, more preferably 10⁸ M⁻¹ or greater, and most preferably 10⁹ M⁻¹ or greater. The binding affinity of an antibody can be readily determined by one of ordinary skill in the art, for example, by Scatchard analysis (Scatchard, G., Ann. NY Acad. Sci. 51: 660-672, 1949).

Second, antibodies are determined to specifically bind if they do not significantly cross-react with related polypeptides. Antibodies do not significantly cross-react with related polypeptide molecules, for example, if they detect human PC4 but not known related polypeptides using a standard Western blot analysis (Ausubel et al., ibid.). Examples of known related polypeptides are orthologs (e.g., murine PC4), and paralogs such as other known human prohormone convertases (e.g. PC1 and PC2), or mutant human PC4 polypeptides, and non-mammalian prohormone convertases (e.g., subtilisin, or Kex2). Moreover, antibodies may be "screened against" known related polypeptides to isolate a population that specifically binds to the inventive polypeptides. For example, antibodies raised to human PC4 are adsorbed to related polypeptides adhered to inspluble matrix; antibodies specific to human PC4 will flow through the matrix under the proper buffer conditions. Such screening allows isolation of polyclonal and monoclonal antibodies non-crossreactive to closely related polypeptides (Antibodies: A Laboratory Manual, Harlow and Lane (eds.), Cold Spring Harbor Laboratory Press, 1988; Current Protocols in Immunology, Cooligan, et al. (eds.), National Institutes of Health, John Wiley and Sons, Inc., 1995). Screening and isolation of specific antibodies is well known in the art. See, Fundamental Immunology, Paul (eds.), Raven Press, 1993; Getzoff et al., Adv. in Immunol. 43: 1-98, 1988; Monoclonal Antibodies: Principles and Practice, Goding, J. W. (eds.), Academic Press Ltd., 1996; Benjamin et al., Ann. Rev. Immunol. 2: 67-101, 1984.

A variety of assays known to those skilled in the art can be utilized to detect and purify antibodies which specifically bind to human PC4 proteins or peptides. Exemplary assays are described in detail in Antibodies: A Laboratory Manual, Harlow and Lane (Eds.), Cold Spring Harbor Laboratory Press, 1988. Representative examples of such assays include: concurrent immunoelectrophoresis, radioimmunoassay, radioimmuno-precipitation, enzyme-linked immunosorbent assay (ELISA), dot blot or Western blot assay, inhibition or competition assay, and sandwich assay.

In addition, antibodies can be screened for binding to wild-type versus mutant human PC4 protein or polypeptide. Antibodies to human PC4 may be used for tagging cells that express human PC4; for isolating human PC4 by affinity purification; for diagnostic assays for determining levels of human prohormone convertase 4 polypeptides in cell and tissue lysates in vitro and in vivo; for in situ immunolocalization to determine tissue distribution in vivo; for detecting or quantitating human prohormone convertase 4 proteins as a marker of underlying pathology or disease; in analytical methods employing a flow cytometer or FACS; for screening expression libraries; for generating anti-idiotypic antibodies; and as neutralizing antibodies; or as antagonists to block human PC4 catalytic activity in vitro and in vivo. Methods for utilizing antibodies in this manner are well known in the art. Suitable direct tags or labels include radionuclides, enzymes, substrates, cofactors, inhibitors, fluorescent markers, chemiluminescent markers, magnetic particles and the like; indirect tags or labels may feature use of biotin-avidin or other complement/anti-complement pairs as intermediates. Antibodies herein may also be directly or indirectly conjugated to drugs, toxins, radionuclides and the like, and these conjugates used for in vivo diagnostic or therapeutic applications. Moreover, antibodies to human PC4 or fragments thereof may be used in vitro to detect denatured human PC4 or fragments thereof in assays, for example, Western Blots or other assays known in the art.

A testis-specific processing enzyme, such as human prohormone convertase 4, is involved in processing prohormones or binding proteins expressed by testicular cells. Thus, human prohormone convertase 4 may be useful in identifying and determining the biological function of testicular prohormones and identifying novel prohormones as discussed below. In support of the proposition that human PC4 may play a role in fertility, and/or testicular function related to spermatogenesis, is a recent paper describing that homozygous male murine PC4 mutant mice have severely impaired fertility (Mbikay, M., et al., Proc. Natl. Acad. Sci., 94:6842-6846, 1997. Moreover, the authors observed no apparent spermatogenic abnormalities in these mutant mice, and that eggs fertilized by these sperm failed to grow to the blastocyst stage, suggesting not only a role in fertilization but in early embryonic development. Proteins of the present invention are used to process or partially process known or unknown prohormone polypeptides to their mature or biologically active forms, which may, for example, stimulate proliferation or differentiation of testicular cells. Moreover, proteins of the present invention, their antagonists and agonists, may play a role in male fertility. To test whether human PC4 acts on a substrate, potential prohormone polypeptide substrates may be co-expressed in the same cell as human PC4 or by combined with human PC4 in vitro. Methods to construct such a cell or combine proteins in vitro are known in the art and disclosed herein. Cleavage products result from human PC4 activity on potential prohormone substrates. Activity of the proteins of the present invention can be measured by assaying a biological activity associated with cleavage products of a prohormone precursor polypeptide cleaved by prohormone convertase 4. In addition, if biological activity of a cleavage product cannot be measured, other methods, such as Western Blot, can be used to determine whether human PC4 has cleaved the substrate prohormone.

Polypeptides of the present invention can be used to determine polypeptide prohormone substrates of a human prohormone convertase 4. Using methods well known in the art, a cell can be cultured, into which has been introduced an expression vector that expresses the mature form of human prohormone convertase 4 and co-expresses a test substrate prohormone polypeptide. Cleavage products resulting from cleavage of the test substrate by the human prohormone convertase 4 can be measured by a biological or biochemical assay described herein. Moreover, such a method of determining polypeptide prohormone substrates of a human prohormone convertase 4 polypeptide can be determined in vitro. Isolated or purified human prohormone convertase 4 polypeptide or lysates from cells expressing human prohormone convertase 4 can be combined in vitro with a test substrate polypeptide such as a test substrate prohormone polypeptide or a synthetic polypeptide which contain a dibasic cleavage site. Cleavage products resulting from cleavage of the test substrate prohormone polypeptide by the human prohormone convertase 4 polypeptide can be detected by a biological or biochemical assay described herein.

Various assays may be used to determine the biological activity of cleavage products. For example, proliferation and differentiation can be measured using cultured testicular cells or in vivo by administering prohormone molecules cleaved or processed by polypeptides of the present invention to the appropriate animal model. Cultured testicular cells include dolphin DB1.Tes cells (CRL-6258); mouse GC-1 spg cells (CRL-2053); TM3 cells (CRL-1714); TM4 cells (CRL-1715); and pig ST cells (CRL-1746), available from American Type Culture Collection, Rockville, Md. Assays measuring cell proliferation or differentiation are well known in the art. For example, assays measuring proliferation include such assays as chemosensitivity to neutral red dye (Cavanaugh et al., Investigational New Drugs 8:347-354, 1990), incorporation of radiolabeled nucleotides (Cook et al., Analytical Biochem. 179:1-7, 1989), incorporation of 5-bromo-2'-deoxyuridine (BrdU) in the DNA of proliferating cells (Porstmann et al., J. Immunol. Methods 82:169-179, 1985), and use of tetrazolium salts (Mosmann, J. Immunol. Methods 65:55-63, 1983; Alley et al., Cancer Res. 48:589-601, 1988; Marshall et al., Growth Reg. 5:69-84, 1995; and Scudiero et al., Cancer Res. 48:4827-4833, 1988). Assays measuring differentiation include, for example, measuring cell-surface markers associated with stage-specific expression of a tissue, enzymatic activity, functional activity or morphological changes (Watt, FASEB, 5:281-284, 1991; Francis, Differentiation 57:63-75, 1994; Raes, Adv. Anim. Cell Biol. Technol. Bioprocesses, 161-171, ESACT, 9th meeting, 1989).

In vivo assays for evaluating the effect of human prohormone convertase 4 on testes polypeptide factors are well known in the art. For example, cleavage products can be injected intraperitoneally for a specific time duration. After the treatment period, animals are sacrificed and testes removed and weighed. Testicles are homogenized and sperm head counts are made (Meistrich et al., Exp. Cell Res. 99:72-78, 1976).

Other activities, for example, chemotactic activity, that may be associated with cleavage products of polypeptides processed by a protein of the present invention can also be analyzed. For example, late stage factors in spermatogenesis may be involved in sperm-egg interactions and sperm motility. Assays evaluating such activities are known (Fuchs, Zentralbl Gynakol 11:117-120, 1993; Neurwinger et al., Andrologia 22:335-339, 1990; Harris et al., Human Reprod. 3:856-860, 1988; and Jockenhovel, Andrologica 22:171-178, 1990).

In addition, standard biochemical assay techniques, such as western blot, can be used to detect cleavage products resulting from human PC4 processing of substrate prohormones of unknown activity (Sambrook et al., ibid. and Ausubel, et. al., ibid.). Using such methods, cleavage products secreted from cells expressing human PC4 and the test prohormone substrate can be detected by assaying the medium collected from the cells.

Proteins of the present invention are also used in a cell-based screen for modulators of human prohormone convertase 4. Modulators, such as antagonists and agonists, can affect the prohormone convertase in several ways, e.g. catalytic activity, gene expression, or interaction with substrate polypeptides. Such antagonists and agonists would affect the inventive prohormone convertase by respectively decreasing or increasing cleavage activity of human PC4. This increase or decrease is measured by assessing cleavage products from prohormones on which human PC4 acts. In such application, an indicator prohormone substrate, known to be cleaved by polypeptides of the present invention, is expressed in the same cell expressing the human prohormone convertase 4. Methods to construct such a cell are known in the art and disclosed herein. Preferred indicator prohormone polypeptides are secreted from the cell when processed by the prohormone convertase and have a readily measurable biological activity associated with cleavage products. Examples of such activity assays are disclosed above. Antagonists and agonists are identified by screening the resulting cleavage products secreted from the cells after exposure to the presence of various agents discussed below. Changes in the processing of the indicator substrate reflect activities that the agents have on the human PC4 proteins of the present invention by either enhancing or inhibiting the prohormone convertase, relative to control cells not subjected to the agent. For example, relative to the control, an agonist increasing the activity of human PC4 would result in increased cleavage, and hence more biologically active cleavage products from the indicator substrate. Conversely, relative to the control, an antagonist decreasing the activity of human PC4 would result in decreased cleavage, and hence fewer, or potentially no, biologically active cleavage products from the indicator substrate. Sources for agents that may modulate human PC4, and could be evaluated or used in a test sample, include, but are not limited to, any natural or chemical source including but not limited to plant, microbial and fungal extracts, chemical libraries, and combinatorial chemical libraries. Methods of establishing and employing this type of cell-based screening assay are known in the art.

This type of cell-based screening can be used to detect, in a test sample, the presence of a modulator of human prohormone convertase polypeptide activity. A cell which expresses mature human PC4 protein and co-expresses a known indicator prohormone polypeptide substrate, can be cultured in the presence and absence of a test sample. Construction of such a cell can be achieved by methods known in the art and described herein. For example, an expression vector directing the expression of the mature human PC4 protein and an expression vector directing the expression of a known indicator prohormone polypeptide substrate can be introduced into the same cell. The cell in the absence of a test sample serves as a control, against which the activity of the molecule in the presence of a test sample is compared. Using a biological or biochemical assay, levels of cleavage products resulting from cleavage of the substrate by the human prohormone convertase 4 can be compared in the presence and absence of the test sample. From this comparison, the presence of a modulator of human prohormone convertase activity in the test sample can be elucidated as described above.

Polynucleotides of the present invention are also used to detect abnormalities on human chromosome 19 associated with disease or other human traits. The polynucleotides of the present invention map to the 19p13.3 region on human chromosome 19. Detectable chromosomal aberrations at the prohormone convertase gene locus include but are not limited to aneuploidy, gene copy number changes, insertions, deletions, restriction site changes and rearrangements. Such aberrations can be detected using polynucleotides of the present invention by employing molecular genetic techniques, such as restriction fragment length polymorphism (RFLP) analysis, short tandem repeat (STR) analysis employing PCR techniques, and other genetic linkage analysis techniques known in the art (Sambrook et al., ibid.; Ausubel, et. al., ibid.; Marian, A. J., Chest 108: 255-265, 1995).

The present invention also provides reagents for use in diagnostic applications. For example, the human PC4 gene, a probe comprising human PC4 DNA or RNA, or a subsequence thereof can be used to determine if the human PC4 gene is present on chromosome 19 or if a mutation has occurred. Detectable chromosomal aberrations at the human PC4 gene locus include, but are not limited to, aneuploidy, gene copy number changes, insertions, deletions, restriction site changes and rearrangements. These aberrations can occur within the coding sequence, within introns, or within flanking sequences, including upstream promoter and regulatory regions, and may be manifested as physical alterations within a coding sequence or changes in gene expression level. Analytical probes will generally be at least 20 nucleotides in length, although somewhat shorter probes (14-17 nucleotides) can be used. PCR primers are at least 5 nucleotides in length, preferably 15 or more nt, more preferably 20-30 nt. Short polynucleotides can be used when a small region of the gene is targeted for analysis. For gross analysis of genes, a polynucleotide probe may comprise an entire exon or more. Probes will generally comprise a polynucleotide linked to a signal-generating moiety such as a radio-labeled nucleotide. In general, these diagnostic methods comprise the steps of (a) obtaining a genetic sample from a patient; (b) incubating the genetic sample with a polynucleotide probe or primer as disclosed above, under conditions wherein the polynucleotide will hybridize to complementary polynucleotide sequence, to produce a first reaction product; and (iii) comparing the first reaction product to a control reaction product. A difference between the first reaction product and the control reaction product is indicative of a genetic abnormality in the patient.

Genetic samples for use within the present invention include genomic DNA, cDNA, and RNA. The polynucleotide probe or primer can be RNA or DNA, and will comprise a portion of SEQ ID NO:1, the complement of SEQ ID NO:1, or an RNA equivalent thereof. Suitable assay methods in this regard include molecular genetic techniques known to those in the art, such as restriction fragment length polymorphism (RFLP) analysis, short tandem repeat (STR) analysis employing PCR techniques, ligation chain reaction (Barany, PCR Methods and Applications 1:5-16, 1991), ribonuclease protection assays, and other genetic linkage analysis techniques known in the art (Sambrook et al., ibid.; Ausubel et. al., ibid.; A. J. Marian, ibid., 1995). Ribonuclease protection assays (see, e.g., Ausubel et al., ibid., ch. 4) comprise the hybridization of an RNA probe to a patient RNA sample, after which the reaction product (RNA--RNA hybrid) is exposed to RNase. Hybridized regions of the RNA are protected from digestion. Within PCR assays, a patient genetic sample is incubated with a pair of polynucleotide primers, and the region between the primers is amplified and recovered. Changes in size or amount of recovered product are indicative of mutations in the patient. Another PCR-based technique that can be employed is single strand conformational polymorphism (SSCP) analysis (Hayashi, PCR Methods and Applications 1:34-38, 1991)

EXAMPLES Example 1 Cloning of human prohormone convertase 4

A. Summary

Screening of a human testis cDNA library with a murine PC4 cDNA probe revealed an isolated cDNA, clone pSLHPC4-5, that is homologous to murine PC4 cDNA. This cDNA encoded a human prohormone convertase 4 (human PC4).

B. Preparation of human testis cDNA library

A full-length human PC4 cDNA was obtained by screening a λZAP® II (Stratagene, La Jolla, Calif.) human testis cDNA library. The construction of the testis cDNA library was as follows:

The first strand cDNA reaction contained 15 μl of human testis twice poly d(T)-selected poly (A)⁺ mRNA (Clontech Laboratories) at a concentration of 1.0 μg/μl, and 3 μl of 20 pmole/μl first strand primer ZC6091 (SEQ ID NO:5) containing an Xho I restriction site. The mixture was heated at 70° C. for 4 minutes and cooled by chilling on ice. First strand cDNA synthesis was initiated by the addition of 12 μl of first strand buffer (5× SUPERSCRIPT™ buffer; Life Technologies, Gaithersburg, Md.), 6 μl of 100 mM dithiothreitol, and 3 μl of a deoxynucleotide triphosphate solution containing 10 mM each of dTTP, dATP, dGTP and 5-methyl-dCTP (Pharmacia LKB Biotechnology, Piscataway, N.J.) to the RNA-primer mixture. The reaction mixture was incubated at 37° C. for 2 minutes, followed by the addition of 15 μl of 200 U/μl RNase H⁻ reverse transcriptase (SUPERSCRIPT II®; Life Technologies). The efficiency of the first strand synthesis was analyzed in a parallel reaction by the addition of 5 μCi of ³² P-αdCTP to a 5 μl aliquot from one of the reaction mixtures to label the reaction for analysis. The reactions were incubated at 37° C. for 10 minutes, 45° C. for 1 hour, then incubated at 50° C. for 10 minutes. Unincorporated ³² P-αdCTP in the labeled reaction was removed by chromatography on a 400 pore size gel filtration column (Clontech Laboratories). The unicorporated nucleotides and primers in the unlabeled first strand reactions were removed by chromatography on 400 pore size gel filtration column (Clontech Laboratories). The length of labeled first strand cDNA was determined by agarose gel electrophoresis.

The second strand reaction contained 120 μl of the unlabeled first strand cDNA, 36 μl of 5× polymerase I buffer (125 mM Tris: HCl, pH 7.5, 500 mM KCl, 25 mM MgCl₂, 50 mM (NH₄) ₂ SO₄)), 2.4 μl of 100 mM dithiothreitol, 3.6 μl of a solution containing 10 mM of each deoxynucleotide triphosphate, 6 μl of 5 mM β-NAD, 3.6 μl of 3 U/μl E. coli DNA ligase (New England Biolabs; Beverly, Mass.), 9 μl of 10 U/μl E. coli DNA polymerase I (New England Biolabs), and 1.8 μl of 2 U/μl RNase H (Life Technologies). A 10 μl aliquot from one of the second strand synthesis reactions was labeled by the addition of 10 μCi ³² P-αdCTP to monitor the efficiency of second strand synthesis. The reactions were incubated at 16° C. for two hours, followed by the addition of 15 μl T4 DNA polymerase (10 U/μl, Boerhinger Mannheim, Indianapolis, Ind.) and incubated for an additional 5 minutes at 16° C. Unincorporated ³² P-αdCTP in the labeled reaction was removed by chromatography through a 400 pore size gel filtration column (Clontech Laboratories) before analysis by agarose gel electrophoresis. The reaction was terminated by the addition of 20 μl 0.5 EDTA and extraction with phenol/chloroform and chloroform followed by ethanol precipitation in the presence of 2.5 M ammonium acetate and 4 μg of glycogen carrier. The yield of cDNA was estimated to be approximately 3 μg from starting mRNA template of 15 μg.

Eco RI adapters were ligated onto the 5' ends of the cDNA described above to enable cloning into an expression vector. A 10 μl aliquot of cDNA (˜1.5 μg) and 5 μl of 65 pmole/μl of Eco RI adapter (Pharmacia LKB Biotechnology Inc.) were mixed with 2 μl 10× ligase buffer (660 mM Tris-HCl pH 7.5, 100 MM MgCl₂), 2 μl of 10 mM ATP and 1 μl of 15 U/μl T4 DNA ligase (Promega Corp., Madison, Wis.). The reaction was incubated 2 hours at 5° C., two hours at 7.5° C., 2 hours at 10° C., and 10 hours at 12.5° C. The reaction was terminated by incubation at 70° C. for 20 minutes.

To facilitate the directional cloning of the cDNA into a lZapII® vector (Stratagene), the cDNA was digested with Xho I, resulting in a cDNA having a 5' Eco RI cohesive end and a 3' Xho I cohesive end. The Xho I restriction site at the 3' end of the cDNA had been previously introduced using the ZC6091 primer (SEQ ID NO:5). Restriction enzyme digestion was carried out in a reaction mixture containing 20 μl of cDNA described above, 10 μl of 10× H Buffer (Boehringer Mannheim), 69 μl H₂ O, and 1.0 μl of 40 U/μl Xho I (Boehringer Mannheim). Digestion was carried out at 37° C. for 40 minutes. The reaction was terminated by incubation at 70° C. for 10 minutes and chromatography through a 400 pore size gel filtration column (Clontech Laboratories).

The cDNA was ethanol precipitated, washed with 70% ethanol, air dried and resuspended in 14 μl H₂ O, 2 μl of ligase buffer (Promega Corp., Madison Wis.), 2 μl T4 polynucleotide kinase (10 U/μl, Life Technologies). Following incubation at 37° C. for 30 minutes, the cDNA was heated to 65° C. for 5 minutes, cooled on ice, and electrophoresed on a 0.8% low melt agarose gel. The contaminating adapters and cDNA below 0.6 Kb in length were excised from the gel. The electrodes were reversed, and the cDNA was electrophoresed until concentrated near the lane origin. The area of the gel containing the concentrated cDNA was excised and placed in a microfuge tube, and the approximate volume of the gel slice was determined. An aliquot of water approximately three times the volume of the gel slice (300 μl) and 35 μl 10× β-agarose I buffer (New England Biolabs) was added to the tube, and the agarose was melted by heating to 65° C. for 15 minutes. Following equilibration of the sample to 45° C., 3 μl of 1 U/μl β-agarose I (New England Biolabs) was added, and the mixture was incubated for 60 minutes at 45° C. to digest the agarose. After incubation, 40 μl of 3 M Na acetate was added to the sample, and the mixture was incubated on ice for 15 minutes. The sample was centrifuged at 14,000×g for 15 minutes at room temperature to remove undigested agarose. The cDNA was ethanol precipitated, washed in 70% ethanol, air-dried and resuspended in 10 μl water.

The resulting cDNA was cloned into the lambda phage vector λZap® II (Stratagene) that was predigested with Eco RI and Xho I and dephosphorylated. Ligation of the cDNA to the λZap® II vector was carried out in a reaction mixture containing 1.0 μl of prepared vector, 1.0 μl of human testis cDNA, 1.0 μl 10× Ligase Buffer (Promega Corp.), 1.0 μl of 10 mM ATP, 5 μl H₂ O, and 1.0 μl of T4 DNA Ligase at 15 units/μl (Promega Corp.). The ligation mixture was incubated at 5° C.-15° C. overnight in a temperature gradient. After incubation, the ligation mixture was packaged into phage using an in vi tro packaging extract (Gigapack® III Gold packaging extract; Stratagene), and the resulting library was titered according to the manufacturer's specifications.

C. Isolation of polynucleotide

The human testis λZap® II library was used to infect E. coli host cells (XL1-Blue™ MRF' strain; Stratagene), and 1.5×10⁶ pfu were plated onto 150-mm NZY plates at a density of ˜40,000 pfu/plate. The inoculated plates were incubated overnight at 37° C. Filter plaques lifts were made using nylon membranes (Hybond™; Amersham Corp., Arlington Heights, Ill.), according to the procedures provided by the manufacturer. The filters were processed by denaturation in solution containing 1.5 M NaCl and 0.5 M NaOH for 7 minutes at room temperature. The filters were blotted briefly on filter paper to remove excess denaturation solution, followed by neutralization for 5 minutes in 1 M Tris-HCl, pH 7.5, and 1.5 M NaCl. Phage DNA was fixed onto the filters with 1,200 μJoules of UV energy in a UV Crosslinker (Stratalinker®; Stratagene). After fixing, the filters were prehybridized in hybridization solution (5× SSC, 5× Denhardt's solution, 0.2% SDS and 1 mM EDTA). Heat denatured, sheared salmon sperm DNA at a final concentration of 100 μg/ml was added. The filters were prehybridized at 65° C. overnight.

A probe was prepared as a PCR product by using oligonucleotide to amplify the rat prohormone convertase cDNA coding region corresponding to nucleotide-45 to nucleotide 1033 of SEQ ID NO:6. An initial, first-round PCR reaction mixture contained 2 μl of ZC11,808 (SEQ ID NO:7) and 2 μl of ZC11,809 (SEQ ID NO:8), 1 μl of 400 femptogram/μl rat testis cDNA, 1 μl of 10 mM dNTP, 10 μl of 10× Klentaq buffer (Clontech), 83 μl water, and 2 μl Klentaq DNA polymerase (Clontech). The first-round PCR reaction was run as follows: initial 95° C. for 30 seconds;

then 30 cycles at 95° C. for 30 seconds, 57° C. for 30 seconds, 68° C. for 2 minutes; followed by 68° C. for 10 minutes. The first-round PCR product was diluted 1:2000 with water.

One μl of the diluted first-round PCR product was subjected to a second PCR using nested primers, ZC11,870 (SEQ ID NO:9) and ZC11,871 (SEQ ID NO:10), designed to amplify DNA internal to the first-round PCR product. The second-round PCR reaction was run as follows: initial 95° C. for 30 seconds; then 30 cycles at 95° C. for 30 seconds, 58° C. for 30 seconds, 68° C. for 2 minutes; followed by 68° C. for 10 minutes. The second-round PCR product was gel purified on a 1.5% low melt agarose gel for use as a probe to screen a human testis cDNA library for human PC4.

Twenty-five nanograms PCR product was radiolabeled with a ³² P-dCTP by random priming using the MEGAPRIME™ DNA Labeling System (Amersham), according to the manufacturer's specifications. The prehybridization solution was replaced with fresh hybridization solution containing 6.5×10⁵ cpm/ml labeled probe and allowed to hybridize overnight at 60° C. After hybridization, the hybridization solution was removed, and the filters were rinsed in a wash solution containing 1× SSC, 0.25% SDS and 1 mM EDTA at 45° C. The filters were placed on autoradiograph film and exposed at -70° C. with intensifying screens for 96 hours.

Examination of the autoradiographs revealed multiple regions that hybridized with the labeled probe. Agar plugs were picked from 39 regions for purification. Each agar plug was soaked overnight in 0.5 ml of SM containing 1% (v/v) chloroform (Sambrook et al. Molecular Cloning: A Laboratory Manual, 2nd ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989). After incubation, the phage from each plug were diluted 1:1000 in SM. Aliquots of 50 μl were plated on E. coli XL-1 Blue™ MRF' cells. The plates were incubated overnight at 37° C., and filter lifts were prepared, prehybridized, hybridized, washed and autoradiographed as described above. Examination of the resulting autoradiographs revealed positive signals on 10 filter lifts. Agar plugs were picked from these regions and were subjected to an additional round of plaque purification.

The plasmids were excised using an ExASSIST/SOLR™ system (Stratagene), according to the manufacturer's specification. These plasmids were amplified by PCR for insert size determination and sequencing. A clone, designated pSLHPC4-5, was shown to contain the sequence shown in SEQ ID NO: 1.

Example 2 Tissue Distribution

A probe was prepared from the full length coding sequence of pSLHPC4-5 and used to probe Human Multiple Tissue Northern Blots (Clontech). The Northern analysis revealed a band at approximately 2.8 Kb that was only present in testis.

Example 3 PCR-Based Chromosomal Mapping of the Human PC4 Gene

Human PC4 was mapped to chromosome 19 using the commercially available "GeneBridge 4 Radiation Hybrid Panel" (Research Genetics, Inc., Huntsville, Ala.). The GeneBridge 4 Radiation Hybrid Panel contains DNAs from each of 93 radiation hybrid clones, plus two control DNAs (the HFL donor and the A23 recipient). A publicly available WWW server (http://www-genome.wi.mit.edu/cgi-bin/contig/rhmapper.pl) allows mapping relative to the Whitehead Institute/MIT Center for Genome Research's map of the human genome (the "WICGR" human genomic map) which was constructed with the GeneBridge 4 Radiation Hybrid Panel. B.

For the mapping of human PC4 with the "GeneBridge 4 RH Panel", 20 μl PCR reactions were set up in a 96-well microtiter plate (Stratagene) and used in a "RoboCycler Gradient 96" thermal cycler (Stratagene). Each of the 95 PCR reactions consisted of 2 μl 10× KlenTaq PCR reaction buffer (Clontech Laboratories, Inc., Palo Alto, Calif.), 1.6 μl dNTPs mix (2.5 mM each, Perkin-Elmer, Foster City, Calif.), 1 μl sense primer, ZC13,557 (SEQ ID NO:11), 1 μl antisense primer, ZC13,558 (SEQ ID NO:12), 2 μl "RediLoad" (Research Genetics, Inc., Huntsville, Ala.), 0.4 μl 50× Advantage KlenTaq Polymerase Mix (Clontech Laboratories, Inc.), 25 ng of DNA from an individual hybrid clone or control and ddH₂ O for a total volume of 20 μl. The reactions were overlaid with an equal amount of mineral oil and sealed. The PCR cycler conditions were as follows: an initial 1 cycle 5 minute denaturation at 95° C., cycles of a 1 minute denaturation at 95° C., 1 minute annealing at 68° C. and 1.5 minute extension at 72° C., followed by a final 1 cycle extension of 7 minutes at 72° C. The reactions were separated by electrophoresis on a 3% NuSieve GTG agarose gel (FMC Bioproducts, Rockland, Me.).

The results showed that human PC4 maps 10.54 cR₋₋ 3000 distal from the chromosome 19 framework marker IB1264 on the WICGR radiation hybrid map. This positions human PC4 in the 19pl3.3 region on the integrated LDB chromosome 19 map (The Genetic Location Database, University of Southhampton, www server: http://cedar.genetics.soton.ac.uk/public₋₋ html/).

Example 4 Construction of Human PC4 Mammalian Expression Vector PPC4-5/pHZ1

An expression vector was prepared for expressing the human PC4 polypeptide in mammalian cells. The mammalian expression vector pHZ1 has the neomycin gene under control of the SV40 early promoter, SV40 polyadenylation site, a multiple cloning site (polylinker) to insert the gene of interest under control of the metallothionine (MT-1) promoter, and the human growth hormone (hGH) polyadenylation site. The expression vector is deposited with the American Type Culture Collection, 12301 Parklawn Drive, Rockville, Md.

Human PC4 was subcloned into the EcoRI/XbaI site in the PHZ1 polylinker. The vector fragment was prepared by cleaving PHZl with EcoRI and XbaI (Boehringer-Mannheim) followed by fragment isolation via Qiaquick™ column (Qiagen). A 1644 bp fragment (5' fragment) was excised from the human PC4 clone in Example 1 with restriction enzymes EcoRI and AatII which gives the 5' end of the human PC4 sequence including 5' UTRs as disclosed in SEQ ID NO:1. An approximately 681 bp PCR fragment was PCR-amplified from the human PC4 clone in Example 1 with primer ZC13,359 (SEQ ID NO:13) which spans the human PC4 AatII site and primer ZC13,358 (SEQ ID NO:14) which contains a XbaI site, giving the 3' end of the human PC4 sequence including 3' UTRs as disclosed in SEQ ID NO:1. The PCR reaction conditions were: one cycle at 94° C. for 1 35 minute; then 35 cycles at 94° C. for 30 seconds, 50° C. for 20 seconds, 72° C. for 30 seconds; followed by one cycle at 72° C. for 10 minutes. The PCR product was cleaved with AatII and XbaI, and fragment purified as described above, generating the 681 bp PCR fragment (3' fragment).

The excised 5' fragment and 3' fragment DNA was subcloned into the pHZI vector fragment. Approximately 20 nanograms of the Eco RI/AatII digested human PC4 5' fragment, approximately 20 nanograms of the AatII/XbaI digested human PC4 3' fragment, and approximately 40 ng of the corresponding vector fragment were ligated 5 hours at room temperature, under standard ligation reaction buffer conditions. Of this ligation reaction, 1 μl was electroporated into 25 μl DHIOB competent cells (GIBCO BRL, Gaithersburg, Md.) according to manufacturer's instructions, plated onto LB plates containing 100 mg/ml ampicillin and incubated overnight at 37° C.

Colonies were screened by PCR using primers ZC12,634 (SEQ ID NO:15) and ZC12,945 (SEQ ID NO:16) under the following PCR conditions: one cycle at 94° C. for 1 minute; then 25 cycles at 94° C. for 20 seconds, 50° C. for 30 seconds, 72° C. for 1 minute; followed by one cycle at 72° C. for 10 minutes. The insert sequence of positive clones were verified by sequence analysis. Large scale plasmid preparation was done using a QIAGEN® Maxi prep kit (Qiagen) according to manufacturer's instructions.

From the foregoing, it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

    __________________________________________________________________________     #             SEQUENCE LISTING                                                 - <160> NUMBER OF SEQ ID NOS: 16                                               - <210> SEQ ID NO 1                                                            <211> LENGTH: 2744                                                             <212> TYPE: DNA                                                                <213> ORGANISM: Homo sapiens                                                   <220> FEATURE:                                                                 <221> NAME/KEY: CDS                                                            <222> LOCATION: (61)...(2325)                                                  - <400> SEQUENCE: 1                                                            - gaattcggca cgaggcggga gggaggggat ttgcgcaggc cccgctcccg cc - #ccgcctcc          60                                                                           - atg cgg ccc gcc ccg att gcg ctg tgg ctg cg - #c ctg gtc ttg gcc ctg           108                                                                           Met Arg Pro Ala Pro Ile Ala Leu Trp Leu Ar - #g Leu Val Leu Ala Leu            #                 15                                                           - gcc ctt gtc cgc ccc cgg gct gtg ggg tgg gc - #c ccg gtc cga gcc ccc           156                                                                           Ala Leu Val Arg Pro Arg Ala Val Gly Trp Al - #a Pro Val Arg Ala Pro            #             30                                                               - atc tat gtc agc agc tgg gcc gtc cag gtg tc - #c cag ggt aac cgg gag           204                                                                           Ile Tyr Val Ser Ser Trp Ala Val Gln Val Se - #r Gln Gly Asn Arg Glu            #         45                                                                   - gtc gag cgc ctg gca cgc aaa ttc ggc ttc gt - #c aac ctg ggg ccg atc           252                                                                           Val Glu Arg Leu Ala Arg Lys Phe Gly Phe Va - #l Asn Leu Gly Pro Ile            #     60                                                                       - ttc cct gac ggg cag tac ttt cac ctg cgg ca - #c cgg ggc gtg gtc cag           300                                                                           Phe Pro Asp Gly Gln Tyr Phe His Leu Arg Hi - #s Arg Gly Val Val Gln            # 80                                                                           - cag tcc ctg acc ccg cac tgg ggc cac cgc ct - #g cac ctg aag aaa aac           348                                                                           Gln Ser Leu Thr Pro His Trp Gly His Arg Le - #u His Leu Lys Lys Asn            #                 95                                                           - ccc aag gtg cag tgg ttc cag cag cag acg ct - #g cag cgg cgg gtg aaa           396                                                                           Pro Lys Val Gln Trp Phe Gln Gln Gln Thr Le - #u Gln Arg Arg Val Lys            #           110                                                                - cgc tct gtc gtg gtg ccc acg gac ccc tgg tt - #c tcc aag cag tgg tac           444                                                                           Arg Ser Val Val Val Pro Thr Asp Pro Trp Ph - #e Ser Lys Gln Trp Tyr            #       125                                                                    - atg aac agc gag gcc caa cca gac ctg agc at - #c ctg cag gcc tgg agt           492                                                                           Met Asn Ser Glu Ala Gln Pro Asp Leu Ser Il - #e Leu Gln Ala Trp Ser            #   140                                                                        - cag ggg ctg tca ggc cag ggc atc gtg gtc tc - #t gtg ctg gac gat ggc           540                                                                           Gln Gly Leu Ser Gly Gln Gly Ile Val Val Se - #r Val Leu Asp Asp Gly            145                 1 - #50                 1 - #55                 1 -        #60                                                                            - atc gag aag gac cac ccg gac ctc tgg gcc aa - #c tac gac ccc ctg gcc           588                                                                           Ile Glu Lys Asp His Pro Asp Leu Trp Ala As - #n Tyr Asp Pro Leu Ala            #               175                                                            - agc tat gac ttc aat gac tac gac ccg gac cc - #c cag ccc cgc tac acc           636                                                                           Ser Tyr Asp Phe Asn Asp Tyr Asp Pro Asp Pr - #o Gln Pro Arg Tyr Thr            #           190                                                                - ccc agc aaa gag aac cgg cac ggg acc cgc tg - #t gct ggg gag gtg gcc           684                                                                           Pro Ser Lys Glu Asn Arg His Gly Thr Arg Cy - #s Ala Gly Glu Val Ala            #       205                                                                    - gcg atg gcc aac aat ggc ttc tgt ggt gtg gg - #g gtc gct ttc aac gcc           732                                                                           Ala Met Ala Asn Asn Gly Phe Cys Gly Val Gl - #y Val Ala Phe Asn Ala            #   220                                                                        - cga atc gga ggc gta cgg atg ctg gac ggt ac - #c atc acc gat gtc atc           780                                                                           Arg Ile Gly Gly Val Arg Met Leu Asp Gly Th - #r Ile Thr Asp Val Ile            225                 2 - #30                 2 - #35                 2 -        #40                                                                            - gag gcc cag tcg ctg agc ctg cag ccg cag ca - #c atc cac att tac agc           828                                                                           Glu Ala Gln Ser Leu Ser Leu Gln Pro Gln Hi - #s Ile His Ile Tyr Ser            #               255                                                            - gcc agc tgg ggt ccc gag gac gac ggc cgc ac - #g gtg gac ggc ccc ggc           876                                                                           Ala Ser Trp Gly Pro Glu Asp Asp Gly Arg Th - #r Val Asp Gly Pro Gly            #           270                                                                - atc ctc acc cgc gag gcc ttc cgg cgt ggt gt - #g acc aag ggc cgc ggc           924                                                                           Ile Leu Thr Arg Glu Ala Phe Arg Arg Gly Va - #l Thr Lys Gly Arg Gly            #       285                                                                    - ggg ctg ggc acg ctc ttc atc tgg gcc tcg gg - #c aac ggc ggc ctg cac           972                                                                           Gly Leu Gly Thr Leu Phe Ile Trp Ala Ser Gl - #y Asn Gly Gly Leu His            #   300                                                                        - tac gac aac tgc aac tgc gac ggc tac acc aa - #c agc atc cac acg ctt          1020                                                                           Tyr Asp Asn Cys Asn Cys Asp Gly Tyr Thr As - #n Ser Ile His Thr Leu            305                 3 - #10                 3 - #15                 3 -        #20                                                                            - tcc gtg ggc agc acc acc cag cag ggc cgc gt - #g ccc tgg tac agc gaa          1068                                                                           Ser Val Gly Ser Thr Thr Gln Gln Gly Arg Va - #l Pro Trp Tyr Ser Glu            #               335                                                            - gcc tgc gcc tcc acc ctc acc acc acc tac ag - #c agc ggc gtg gcc acc          1116                                                                           Ala Cys Ala Ser Thr Leu Thr Thr Thr Tyr Se - #r Ser Gly Val Ala Thr            #           350                                                                - gac ccc cag atc gtc acc acg gac ctg cat ca - #c ggg tgc aca gac cag          1164                                                                           Asp Pro Gln Ile Val Thr Thr Asp Leu His Hi - #s Gly Cys Thr Asp Gln            #       365                                                                    - cac acg ggc acc tcg gcc tca gcc cca ctg gc - #g gcc ggc atg atc gcc          1212                                                                           His Thr Gly Thr Ser Ala Ser Ala Pro Leu Al - #a Ala Gly Met Ile Ala            #   380                                                                        - cta gcg ctg gag gcc aac ccg ttc ctg acg tg - #g aga gac atg cag cac          1260                                                                           Leu Ala Leu Glu Ala Asn Pro Phe Leu Thr Tr - #p Arg Asp Met Gln His            385                 3 - #90                 3 - #95                 4 -        #00                                                                            - ctg gtg gtc cgc gcg tcc aag ccg gcg cac ct - #g cag gcc gag gac tgg          1308                                                                           Leu Val Val Arg Ala Ser Lys Pro Ala His Le - #u Gln Ala Glu Asp Trp            #               415                                                            - agg acc aac ggc gtg ggg cgc caa gtg agc ca - #t cac tac gga tac ggg          1356                                                                           Arg Thr Asn Gly Val Gly Arg Gln Val Ser Hi - #s His Tyr Gly Tyr Gly            #           430                                                                - ctg ctg gac gcc ggg ctg ctg gtg gac acc gc - #c cgc acc tgg ctg ccc          1404                                                                           Leu Leu Asp Ala Gly Leu Leu Val Asp Thr Al - #a Arg Thr Trp Leu Pro            #       445                                                                    - acc cag ccg cag agg aag tgc gcc gtc cgg gt - #c cag agc cgc ccc acc          1452                                                                           Thr Gln Pro Gln Arg Lys Cys Ala Val Arg Va - #l Gln Ser Arg Pro Thr            #   460                                                                        - ccc atc ctg ccg ctg atc tac atc agg gaa aa - #c gta tcg gcc tgc gcc          1500                                                                           Pro Ile Leu Pro Leu Ile Tyr Ile Arg Glu As - #n Val Ser Ala Cys Ala            465                 4 - #70                 4 - #75                 4 -        #80                                                                            - ggc ctc cac aac tcc atc cgc tcg ctg gag ca - #c gtg cag gcg cag ctg          1548                                                                           Gly Leu His Asn Ser Ile Arg Ser Leu Glu Hi - #s Val Gln Ala Gln Leu            #               495                                                            - acg ctg tcc tac agc cgg cgc gga gac ctg ga - #g atc tcg ctc acc agc          1596                                                                           Thr Leu Ser Tyr Ser Arg Arg Gly Asp Leu Gl - #u Ile Ser Leu Thr Ser            #           510                                                                - ccc atg ggc acg cgc tcc aca ctc gtg gcc at - #a cga ccc ttg gac gtc          1644                                                                           Pro Met Gly Thr Arg Ser Thr Leu Val Ala Il - #e Arg Pro Leu Asp Val            #       525                                                                    - agc act gaa ggc tac aac aac tgg gtc ttc at - #g tcc acc cac ttc tgg          1692                                                                           Ser Thr Glu Gly Tyr Asn Asn Trp Val Phe Me - #t Ser Thr His Phe Trp            #   540                                                                        - gat gag aac cca cag ggc gtg tgg acc ctg gg - #c cta gag aac aag ggc          1740                                                                           Asp Glu Asn Pro Gln Gly Val Trp Thr Leu Gl - #y Leu Glu Asn Lys Gly            545                 5 - #50                 5 - #55                 5 -        #60                                                                            - tac tat ttc aac acg ggg acg ttg tac cgc ta - #c acg ctg ctg ctc tat          1788                                                                           Tyr Tyr Phe Asn Thr Gly Thr Leu Tyr Arg Ty - #r Thr Leu Leu Leu Tyr            #               575                                                            - ggg acg gcc gag gac atg aca gcg cgg cct ac - #a ggc ccc cag gtg acc          1836                                                                           Gly Thr Ala Glu Asp Met Thr Ala Arg Pro Th - #r Gly Pro Gln Val Thr            #           590                                                                - agc agc gcg tgt gtg cag cgg gac aca gag gg - #g ctg tgc cag gcg tgt          1884                                                                           Ser Ser Ala Cys Val Gln Arg Asp Thr Glu Gl - #y Leu Cys Gln Ala Cys            #       605                                                                    - gac ggc ccc gcc tac atc ctg gga cag ctc tg - #c ctg gcc tac tgc ccc          1932                                                                           Asp Gly Pro Ala Tyr Ile Leu Gly Gln Leu Cy - #s Leu Ala Tyr Cys Pro            #   620                                                                        - ccg cgg ttc ttc aac cac aca agg ctg gtg ac - #c gct ggg cct ggg cac          1980                                                                           Pro Arg Phe Phe Asn His Thr Arg Leu Val Th - #r Ala Gly Pro Gly His            625                 6 - #30                 6 - #35                 6 -        #40                                                                            - acg gcg gcg ccc gcg ctg agg gtc tgc tcc ag - #c tgc cat gcc tcc tgc          2028                                                                           Thr Ala Ala Pro Ala Leu Arg Val Cys Ser Se - #r Cys His Ala Ser Cys            #               655                                                            - tac acc tgc cgc ggc ggc tcc ccg agg gac tg - #c acc tcc tgt ccc cca          2076                                                                           Tyr Thr Cys Arg Gly Gly Ser Pro Arg Asp Cy - #s Thr Ser Cys Pro Pro            #           670                                                                - tcc tcc acg ctg gac cag cag cag ggc tcc tg - #c atg gga ccc acc acc          2124                                                                           Ser Ser Thr Leu Asp Gln Gln Gln Gly Ser Cy - #s Met Gly Pro Thr Thr            #       685                                                                    - ccc gac agc cgc ccc cgg ctt aga gct gcc gc - #c tgt ccc cac cac cgc          2172                                                                           Pro Asp Ser Arg Pro Arg Leu Arg Ala Ala Al - #a Cys Pro His His Arg            #   700                                                                        - tgc cca gcc tcg gcc atg gtg ctg agc ctc ct - #g gcc gtg acc ctc gga          2220                                                                           Cys Pro Ala Ser Ala Met Val Leu Ser Leu Le - #u Ala Val Thr Leu Gly            705                 7 - #10                 7 - #15                 7 -        #20                                                                            - ggc ccc gtc ctc tgc ggc atg tcc atg gac ct - #c cca cta tac gcc tgg          2268                                                                           Gly Pro Val Leu Cys Gly Met Ser Met Asp Le - #u Pro Leu Tyr Ala Trp            #               735                                                            - ctc tcc cgt gcc agg gcc acc ccc acc aaa cc - #c cag gtc tgg ctg cca          2316                                                                           Leu Ser Arg Ala Arg Ala Thr Pro Thr Lys Pr - #o Gln Val Trp Leu Pro            #           750                                                                - gct gga acc tgaagttgtc agctcagaaa gcgaccttgc ccccgcctg - #g                  2365                                                                           Ala Gly Thr                                                                            755                                                                    - gtccctgaca ggcactgctg ccatgctgcc tccccaggct ggccccagag ga - #gcgagcac        2425                                                                           - cagcacccga cgcctggcct gccagggatg ggccccgtgg aaccccgaag cc - #tggcggga        2485                                                                           - gagagagaga gagaagtctc ctctgcattt tgggtttggg cgggagtggg ct - #ggggggag        2545                                                                           - aggctggagc accccaaaag ccaggggaaa gtggagggag agaaacgtga ca - #ctgtccgc        2605                                                                           - ctcgggcacc gcatccaacc tcagagtttg caaataaagg ttgcttagaa gg - #tgaaaaaa        2665                                                                           - aaaaaaaaaa aaaaaaaaaa aaaaaaaaaa aaaaaaaaaa aaaaaaaaaa aa - #aaaaaaaa        2725                                                                           #                 274 - #4                                                     - <210> SEQ ID NO 2                                                            <211> LENGTH: 755                                                              <212> TYPE: PRT                                                                <213> ORGANISM: Homo sapiens                                                   - <400> SEQUENCE: 2                                                            - Met Arg Pro Ala Pro Ile Ala Leu Trp Leu Ar - #g Leu Val Leu Ala Leu          #                15                                                            - Ala Leu Val Arg Pro Arg Ala Val Gly Trp Al - #a Pro Val Arg Ala Pro          #            30                                                                - Ile Tyr Val Ser Ser Trp Ala Val Gln Val Se - #r Gln Gly Asn Arg Glu          #        45                                                                    - Val Glu Arg Leu Ala Arg Lys Phe Gly Phe Va - #l Asn Leu Gly Pro Ile          #    60                                                                        - Phe Pro Asp Gly Gln Tyr Phe His Leu Arg Hi - #s Arg Gly Val Val Gln          #80                                                                            - Gln Ser Leu Thr Pro His Trp Gly His Arg Le - #u His Leu Lys Lys Asn          #                95                                                            - Pro Lys Val Gln Trp Phe Gln Gln Gln Thr Le - #u Gln Arg Arg Val Lys          #           110                                                                - Arg Ser Val Val Val Pro Thr Asp Pro Trp Ph - #e Ser Lys Gln Trp Tyr          #       125                                                                    - Met Asn Ser Glu Ala Gln Pro Asp Leu Ser Il - #e Leu Gln Ala Trp Ser          #   140                                                                        - Gln Gly Leu Ser Gly Gln Gly Ile Val Val Se - #r Val Leu Asp Asp Gly          145                 1 - #50                 1 - #55                 1 -        #60                                                                            - Ile Glu Lys Asp His Pro Asp Leu Trp Ala As - #n Tyr Asp Pro Leu Ala          #               175                                                            - Ser Tyr Asp Phe Asn Asp Tyr Asp Pro Asp Pr - #o Gln Pro Arg Tyr Thr          #           190                                                                - Pro Ser Lys Glu Asn Arg His Gly Thr Arg Cy - #s Ala Gly Glu Val Ala          #       205                                                                    - Ala Met Ala Asn Asn Gly Phe Cys Gly Val Gl - #y Val Ala Phe Asn Ala          #   220                                                                        - Arg Ile Gly Gly Val Arg Met Leu Asp Gly Th - #r Ile Thr Asp Val Ile          225                 2 - #30                 2 - #35                 2 -        #40                                                                            - Glu Ala Gln Ser Leu Ser Leu Gln Pro Gln Hi - #s Ile His Ile Tyr Ser          #               255                                                            - Ala Ser Trp Gly Pro Glu Asp Asp Gly Arg Th - #r Val Asp Gly Pro Gly          #           270                                                                - Ile Leu Thr Arg Glu Ala Phe Arg Arg Gly Va - #l Thr Lys Gly Arg Gly          #       285                                                                    - Gly Leu Gly Thr Leu Phe Ile Trp Ala Ser Gl - #y Asn Gly Gly Leu His          #   300                                                                        - Tyr Asp Asn Cys Asn Cys Asp Gly Tyr Thr As - #n Ser Ile His Thr Leu          305                 3 - #10                 3 - #15                 3 -        #20                                                                            - Ser Val Gly Ser Thr Thr Gln Gln Gly Arg Va - #l Pro Trp Tyr Ser Glu          #               335                                                            - Ala Cys Ala Ser Thr Leu Thr Thr Thr Tyr Se - #r Ser Gly Val Ala Thr          #           350                                                                - Asp Pro Gln Ile Val Thr Thr Asp Leu His Hi - #s Gly Cys Thr Asp Gln          #       365                                                                    - His Thr Gly Thr Ser Ala Ser Ala Pro Leu Al - #a Ala Gly Met Ile Ala          #   380                                                                        - Leu Ala Leu Glu Ala Asn Pro Phe Leu Thr Tr - #p Arg Asp Met Gln His          385                 3 - #90                 3 - #95                 4 -        #00                                                                            - Leu Val Val Arg Ala Ser Lys Pro Ala His Le - #u Gln Ala Glu Asp Trp          #               415                                                            - Arg Thr Asn Gly Val Gly Arg Gln Val Ser Hi - #s His Tyr Gly Tyr Gly          #           430                                                                - Leu Leu Asp Ala Gly Leu Leu Val Asp Thr Al - #a Arg Thr Trp Leu Pro          #       445                                                                    - Thr Gln Pro Gln Arg Lys Cys Ala Val Arg Va - #l Gln Ser Arg Pro Thr          #   460                                                                        - Pro Ile Leu Pro Leu Ile Tyr Ile Arg Glu As - #n Val Ser Ala Cys Ala          465                 4 - #70                 4 - #75                 4 -        #80                                                                            - Gly Leu His Asn Ser Ile Arg Ser Leu Glu Hi - #s Val Gln Ala Gln Leu          #               495                                                            - Thr Leu Ser Tyr Ser Arg Arg Gly Asp Leu Gl - #u Ile Ser Leu Thr Ser          #           510                                                                - Pro Met Gly Thr Arg Ser Thr Leu Val Ala Il - #e Arg Pro Leu Asp Val          #       525                                                                    - Ser Thr Glu Gly Tyr Asn Asn Trp Val Phe Me - #t Ser Thr His Phe Trp          #   540                                                                        - Asp Glu Asn Pro Gln Gly Val Trp Thr Leu Gl - #y Leu Glu Asn Lys Gly          545                 5 - #50                 5 - #55                 5 -        #60                                                                            - Tyr Tyr Phe Asn Thr Gly Thr Leu Tyr Arg Ty - #r Thr Leu Leu Leu Tyr          #               575                                                            - Gly Thr Ala Glu Asp Met Thr Ala Arg Pro Th - #r Gly Pro Gln Val Thr          #           590                                                                - Ser Ser Ala Cys Val Gln Arg Asp Thr Glu Gl - #y Leu Cys Gln Ala Cys          #       605                                                                    - Asp Gly Pro Ala Tyr Ile Leu Gly Gln Leu Cy - #s Leu Ala Tyr Cys Pro          #   620                                                                        - Pro Arg Phe Phe Asn His Thr Arg Leu Val Th - #r Ala Gly Pro Gly His          625                 6 - #30                 6 - #35                 6 -        #40                                                                            - Thr Ala Ala Pro Ala Leu Arg Val Cys Ser Se - #r Cys His Ala Ser Cys          #               655                                                            - Tyr Thr Cys Arg Gly Gly Ser Pro Arg Asp Cy - #s Thr Ser Cys Pro Pro          #           670                                                                - Ser Ser Thr Leu Asp Gln Gln Gln Gly Ser Cy - #s Met Gly Pro Thr Thr          #       685                                                                    - Pro Asp Ser Arg Pro Arg Leu Arg Ala Ala Al - #a Cys Pro His His Arg          #   700                                                                        - Cys Pro Ala Ser Ala Met Val Leu Ser Leu Le - #u Ala Val Thr Leu Gly          705                 7 - #10                 7 - #15                 7 -        #20                                                                            - Gly Pro Val Leu Cys Gly Met Ser Met Asp Le - #u Pro Leu Tyr Ala Trp          #               735                                                            - Leu Ser Arg Ala Arg Ala Thr Pro Thr Lys Pr - #o Gln Val Trp Leu Pro          #           750                                                                - Ala Gly Thr                                                                          755                                                                    - <210> SEQ ID NO 3                                                            <211> LENGTH: 2265                                                             <212> TYPE: DNA                                                                <213> ORGANISM: Artificial Sequence                                            <220> FEATURE:                                                                 <223> OTHER INFORMATION: Degenerate polynucleotide se - #quence for            human                                                                                prohormone convertase 4                                                  <220> FEATURE:                                                                 <221> NAME/KEY: misc.sub.-- feature                                            <222> LOCATION: (1)...(2265)                                                   <223> OTHER INFORMATION: n = A,T,C or G                                        - <400> SEQUENCE: 3                                                            - atgmgnccng cnccnathgc nytntggytn mgnytngtny tngcnytngc ny - #tngtnmgn          60                                                                           - ccnmgngcng tnggntgggc nccngtnmgn gcnccnatht aygtnwsnws nt - #gggcngtn         120                                                                           - cargtnwsnc arggnaaymg ngargtngar mgnytngcnm gnaarttygg nt - #tygtnaay         180                                                                           - ytnggnccna thttyccnga yggncartay ttycayytnm gncaymgngg ng - #tngtncar         240                                                                           - carwsnytna cnccncaytg gggncaymgn ytncayytna araaraaycc na - #argtncar         300                                                                           - tggttycarc arcaracnyt ncarmgnmgn gtnaarmgnw sngtngtngt nc - #cnacngay         360                                                                           - ccntggttyw snaarcartg gtayatgaay wsngargcnc arccngayyt nw - #snathytn         420                                                                           - cargcntggw sncarggnyt nwsnggncar ggnathgtng tnwsngtnyt ng - #aygayggn         480                                                                           - athgaraarg aycayccnga yytntgggcn aaytaygayc cnytngcnws nt - #aygaytty         540                                                                           - aaygaytayg ayccngaycc ncarccnmgn tayacnccnw snaargaraa ym - #gncayggn         600                                                                           - acnmgntgyg cnggngargt ngcngcnatg gcnaayaayg gnttytgygg ng - #tnggngtn         660                                                                           - gcnttyaayg cnmgnathgg nggngtnmgn atgytngayg gnacnathac ng - #aygtnath         720                                                                           - gargcncarw snytnwsnyt ncarccncar cayathcaya thtaywsngc nw - #sntggggn         780                                                                           - ccngargayg ayggnmgnac ngtngayggn ccnggnathy tnacnmgnga rg - #cnttymgn         840                                                                           - mgnggngtna cnaarggnmg nggnggnytn ggnacnytnt tyathtgggc nw - #snggnaay         900                                                                           - ggnggnytnc aytaygayaa ytgyaaytgy gayggntaya cnaaywsnat hc - #ayacnytn         960                                                                           - wsngtnggnw snacnacnca rcarggnmgn gtnccntggt aywsngargc nt - #gygcnwsn        1020                                                                           - acnytnacna cnacntayws nwsnggngtn gcnacngayc cncarathgt na - #cnacngay        1080                                                                           - ytncaycayg gntgyacnga ycarcayacn ggnacnwsng cnwsngcncc ny - #tngcngcn        1140                                                                           - ggnatgathg cnytngcnyt ngargcnaay ccnttyytna cntggmgnga ya - #tgcarcay        1200                                                                           - ytngtngtnm gngcnwsnaa rccngcncay ytncargcng argaytggmg na - #cnaayggn        1260                                                                           - gtnggnmgnc argtnwsnca ycaytayggn tayggnytny tngaygcngg ny - #tnytngtn        1320                                                                           - gayacngcnm gnacntggyt nccnacncar ccncarmgna artgygcngt nm - #gngtncar        1380                                                                           - wsnmgnccna cnccnathyt nccnytnath tayathmgng araaygtnws ng - #cntgygcn        1440                                                                           - ggnytncaya aywsnathmg nwsnytngar caygtncarg cncarytnac ny - #tnwsntay        1500                                                                           - wsnmgnmgng gngayytnga rathwsnytn acnwsnccna tgggnacnmg nw - #snacnytn        1560                                                                           - gtngcnathm gnccnytnga ygtnwsnacn garggntaya ayaaytgggt nt - #tyatgwsn        1620                                                                           - acncayttyt gggaygaraa yccncarggn gtntggacny tnggnytnga ra - #ayaarggn        1680                                                                           - taytayttya ayacnggnac nytntaymgn tayacnytny tnytntaygg na - #cngcngar        1740                                                                           - gayatgacng cnmgnccnac nggnccncar gtnacnwsnw sngcntgygt nc - #armgngay        1800                                                                           - acngarggny tntgycargc ntgygayggn ccngcntaya thytnggnca ry - #tntgyytn        1860                                                                           - gcntaytgyc cnccnmgntt yttyaaycay acnmgnytng tnacngcngg nc - #cnggncay        1920                                                                           - acngcngcnc cngcnytnmg ngtntgywsn wsntgycayg cnwsntgyta ya - #cntgymgn        1980                                                                           - ggnggnwsnc cnmgngaytg yacnwsntgy ccnccnwsnw snacnytnga yc - #arcarcar        2040                                                                           - ggnwsntgya tgggnccnac nacnccngay wsnmgnccnm gnytnmgngc ng - #cngcntgy        2100                                                                           - ccncaycaym gntgyccngc nwsngcnatg gtnytnwsny tnytngcngt na - #cnytnggn        2160                                                                           - ggnccngtny tntgyggnat gwsnatggay ytnccnytnt aygcntggyt nw - #snmgngcn        2220                                                                           #                2265cc ncargtntgg ytnccngcng gnacn                            - <210> SEQ ID NO 4                                                            <211> LENGTH: 5                                                                <212> TYPE: PRT                                                                <213> ORGANISM: Homo sapiens                                                   - <400> SEQUENCE: 4                                                            - Arg Arg Val Lys Arg                                                           1               5                                                             - <210> SEQ ID NO 5                                                            <211> LENGTH: 49                                                               <212> TYPE: DNA                                                                <213> ORGANISM: Artificial Sequence                                            <220> FEATURE:                                                                 <223> OTHER INFORMATION: Oligonucleotide primer ZC609 - #1                     - <400> SEQUENCE: 5                                                            #               49tactc gaggcggccg cttttttttt ttttttttt                        - <210> SEQ ID NO 6                                                            <211> LENGTH: 2458                                                             <212> TYPE: DNA                                                                <213> ORGANISM: Rattus norvegicus                                              - <400> SEQUENCE: 6                                                            - atgcggccct cccagacagc gctgtggctg ggtctggttt tgtctttggc cc - #tcctggct          60                                                                           - gtggggtggg cctcagcccg accacccatc tatgtcagca gctgggcagt gc - #gggtgacc         120                                                                           - aaaggttacc aggaggctga gcgcctggca cgtaaatttg gcttcgtcaa cc - #tgggacag         180                                                                           - atctttcctg atgaccagta tttccatctg aggcaccggg gtgtggccca gc - #agtccctg         240                                                                           - actccgcact ggggccaccg tctgcgcctg aagaaagagc ccaaggtgcg gt - #ggtttgag         300                                                                           - cagcagactt tgaggcggcg ggtgaagcgc tccctggtgg tacccacaga cc - #cctggttt         360                                                                           - tccaagcagt ggtacatgaa caaggagata gaacaagatc tcaacatcct aa - #aggtttgg         420                                                                           - aaccagggac tgactggccg gggagtggtg gtctccatct tggatgatgg ca - #ttgagaag         480                                                                           - gaccatccgg acctctgggc taattatgac cccctggcca gctatgactt ca - #atgattac         540                                                                           - gacccagatc cccagcctcg atacacaccc aacgatgaga accggcatgg aa - #cacgctgc         600                                                                           - gctggggagg tgtctgccac agcaaacaac ggtttctgtg gtgccggtgt gg - #ccttcaat         660                                                                           - gccagaattg gaggcgtgcg catgttggat ggagccatca ctgacatcgt gg - #aggctcag         720                                                                           - tccctcagcc tgcagccgca acacatacac atctatagcg ccagttgggg cc - #ccgaggat         780                                                                           - gatgggcgca cagtggacgg acccggcctc ctcacgcagg aggccttcag gc - #gtggtgta         840                                                                           - accaagggcc gccaagggct gggcacgctg ttcatctggg cctcgggaaa cg - #gtggcctc         900                                                                           - cactacgaca actgcaattg tgacggctac accaacagca tccacacgct gt - #cagtgggc         960                                                                           - agtaccacgc ggcagggccg agtgccctgg tacagcgagg cctgcgcctc ca - #cgttcacc        1020                                                                           - accaccttca gcagcggtgt ggtcaccgac ccacagatcg tcaccacgga cc - #tacaccat        1080                                                                           - caatgcaccg acaagcacac gggcacctcg gcctccgccc cgctggccgc tg - #gcatgatc        1140                                                                           - gccctggcgc tggaggccaa cccgctgctg acctggaggg acctgcagca cc - #tggtggtc        1200                                                                           - cgcgcgtcca ggccggcgca gctgcaggcg gaggactgga ggatcaacgg cg - #tggggcgc        1260                                                                           - caagtgagcc accactatgg ctatgggctg ctggacgcgg ggctgctggt ag - #acctggct        1320                                                                           - cgcgtgtggc tccctactaa gcctcagaag aaatgcacca ttcgggtggt gc - #acacccca        1380                                                                           - acccccatcc tgcctcggat gctggtgcca aagaacgtga ctgtatgctg cg - #atggctcg        1440                                                                           - cgccgccgcc tcatccgctc gctagagcat gttcaggtcc agctgtcgct ct - #cctacagc        1500                                                                           - cgccgcgggg acctggagat cttcctcacc agccccatgg gcacgcgctc ca - #cgcttgtg        1560                                                                           - gccatcagac ccttggatat cagcggccaa ggctacaaca actggatctt ca - #tgtctact        1620                                                                           - cactactggg atgaggaccc gcagggcctg tggaccctgg ggctggagaa ta - #agggctac        1680                                                                           - tattataaca caggaactct gtactactgc acgctgctgc tgtatgggac gg - #cagaggac        1740                                                                           - atgacagcgc ggccccagac cccccaggtg accagctgcg cgcacgcatg tg - #cagaggga        1800                                                                           - cacagagggg ctgtgccagg aaagtcattg tcccctctcc attgtggcag aa - #ctctgcct        1860                                                                           - catctccagc aagcagtggt ggtggctcta cagccacaca cagcagccag tg - #accaaggg        1920                                                                           - acaggacagc tgtcaccctc ctaccacacc tgctcggcag cttgaccagc ga - #ctacactg        1980                                                                           - cctgttccct gcccctcatg ctgggagtgc ttcagagccc ctccaaggct tg - #tcacctct        2040                                                                           - ggcagccatc ctggctatca gtcttgggcc atggtgctgt ccctgctaac ca - #gggccttt        2100                                                                           - ggaaggcccc tcatcttgag gaaggcccac ctctccccag gctggatacc cc - #tggggagc        2160                                                                           - cagagatgcc ccactctcag gacagaaggc cggtacccca aggccctgct cc - #caggccgg        2220                                                                           - gataggaata tgccccagaa ggccacggca gagagctgca tgggtcacgt ga - #cagcccgc        2280                                                                           - agctcagcct cagctgctcc cagtggaaga gacgtttcct cattcttttt gg - #agcaggta        2340                                                                           - tggcagacaa gaggtcagac cacagccacc aaccacctgc cccttccctg tc - #tccaaacc        2400                                                                           - atccccatgt ctaacctcat agttggcaaa taaagttaaa cagaaaaaaa aa - #aaaaaa          2458                                                                           - <210> SEQ ID NO 7                                                            <211> LENGTH: 25                                                               <212> TYPE: DNA                                                                <213> ORGANISM: Artificial Sequence                                            <220> FEATURE:                                                                 <223> OTHER INFORMATION: Oligonucleotide primer ZC11, - #808                   - <400> SEQUENCE: 7                                                            #               25 tgtc tttgg                                                  - <210> SEQ ID NO 8                                                            <211> LENGTH: 24                                                               <212> TYPE: DNA                                                                <213> ORGANISM: Artificial Sequence                                            <220> FEATURE:                                                                 <223> OTHER INFORMATION: Oligonucleotide primer ZC11, - #809                   - <400> SEQUENCE: 8                                                            #                24tccg tggt                                                   - <210> SEQ ID NO 9                                                            <211> LENGTH: 24                                                               <212> TYPE: DNA                                                                <213> ORGANISM: Artificial Sequence                                            <220> FEATURE:                                                                 <223> OTHER INFORMATION: Oligonucleotide primer ZC11, - #870                   - <400> SEQUENCE: 9                                                            #                24gtgg ggtg                                                   - <210> SEQ ID NO 10                                                           <211> LENGTH: 24                                                               <212> TYPE: DNA                                                                <213> ORGANISM: Artificial Sequence                                            <220> FEATURE:                                                                 <223> OTHER INFORMATION: Oligonucleotide primer ZC11, - #871                   - <400> SEQUENCE: 10                                                           #                24gaac gtgg                                                   - <210> SEQ ID NO 11                                                           <211> LENGTH: 26                                                               <212> TYPE: DNA                                                                <213> ORGANISM: Artificial Sequence                                            <220> FEATURE:                                                                 <223> OTHER INFORMATION: Oligonucleotide primer ZC13, - #557                   - <400> SEQUENCE: 11                                                           #              26  acat ttacag                                                 - <210> SEQ ID NO 12                                                           <211> LENGTH: 21                                                               <212> TYPE: DNA                                                                <213> ORGANISM: Artificial Sequence                                            <220> FEATURE:                                                                 <223> OTHER INFORMATION: Oligonucleotide primer ZC13, - #558                   - <400> SEQUENCE: 12                                                           #21                gccg t                                                      - <210> SEQ ID NO 13                                                           <211> LENGTH: 21                                                               <212> TYPE: DNA                                                                <213> ORGANISM: Artificial Sequence                                            <220> FEATURE:                                                                 <223> OTHER INFORMATION: Oligonucleotide primer ZC13, - #359                   - <400> SEQUENCE: 13                                                           #21                cagc a                                                      - <210> SEQ ID NO 14                                                           <211> LENGTH: 30                                                               <212> TYPE: DNA                                                                <213> ORGANISM: Artificial Sequence                                            <220> FEATURE:                                                                 <223> OTHER INFORMATION: Oligonucleotide primer ZC13, - #358                   - <400> SEQUENCE: 14                                                           #           30     ccag ctggcagcca                                             - <210> SEQ ID NO 15                                                           <211> LENGTH: 19                                                               <212> TYPE: DNA                                                                <213> ORGANISM: Artificial Sequence                                            <220> FEATURE:                                                                 <223> OTHER INFORMATION: Oligonucleotide primer ZC12, - #634                   - <400> SEQUENCE: 15                                                           # 19               tac                                                         - <210> SEQ ID NO 16                                                           <211> LENGTH: 19                                                               <212> TYPE: DNA                                                                <213> ORGANISM: Artificial Sequence                                            <220> FEATURE:                                                                 <223> OTHER INFORMATION: Oligonucleotide primer ZC12, - #945                   - <400> SEQUENCE: 16                                                           # 19               ggc                                                         __________________________________________________________________________ 

What is claimed is:
 1. A method of determining polypeptide prohormone substrates of a human prohormone convertase 4 protein comprising:culturing a cell into which has been introduced an expression vector comprising the following operably linked elements: (a) a transcription promoter; (b) a DNA segment encoding a prohormone convertase polypeptide having an amino acid sequence as shown in SEQ ID NO:2 from amino acid number 20 (Arg) to amino acid number 755 (Thr); and (c) a transcription terminator, wherein the cell expresses a human prohormone convertase protein encoded by the DNA segment and co-expresses a test substrate prohormone polypeptide; and detecting cleavage products resulting from cleavage of the test substrate by the human prohormone convertase 4 protein.
 2. A method of determining polypeptide prohormone substrates of a human prohormone convertase 4 protein comprising:combining in vitro with a test substrate polypeptide, an isolated prohormone convertase 4 polypeptide comprising a sequence of amino acid residues selected from the group consisting of: (a) the amino acid sequence as shown in SEQ ID NO:2 from amino acid number 114 (Ser) to amino acid number 443 (Ala); (b) the amino acid sequence as shown in SEQ ID NO:2 from amino acid number 114 (Ser) to amino acid number 755 (Thr); (c) the amino acid sequence as shown in SEQ ID NO:2 from amino acid number 20 (Arg) to amino acid number 755 (Thr); and (d) the amino acid sequence as shown in SEQ ID NO:2 from amino acid number 1 (Met) to amino acid number 755 (Thr); and detecting cleavage products resulting from cleavage of the test substrate by the human prohormone convertase 4 protein.
 3. A method of detecting, in a test sample, the presence of a modulator of human prohormone convertase 4 protein activity, comprising:culturing a cell into which has been introduced an expression vector comprising the following operably linked elements: (a) a transcription promoter; (b) a DNA segment encoding a prohormone convertase polypeptide having an amino acid sequence as shown in SEQ ID NO:2 from amino acid number 20 (Arg) to amino acid number 755 (Thr); and (c) a transcription terminator, wherein the cell expresses the human prohormone convertase protein encoded by the DNA segment and co-expresses a known indicator prohormone polypeptide substrate, in the presence and absence of a test sample; and comparing levels of cleavage products resulting from cleavage of the substrate by the human prohormone convertase, in the presence and absence of the test sample, by a biological or biochemical assay; and determining from the comparison, the presence of the modulator of human prohormone convertase activity in the test sample. 